Making a 'Hydro modded' Casio F-91W Dive Watch
For anyone even slightly ‘into’ watches, the Casio F-91W needs little introduction. It’s the quintessential cheap digital watch. Sold into the Billions and seen on the wrist of everyone from Obama to Osama. (In)famous as having been used as a cheap and accurate timer in IEDs, it’s said anyone wearing one during the War on Terror in an American airport had a higher probability of being pulled over for that extra special attention.
Despite all of that however, it’s not a dive watch, and as mentioned in my previous entry - I like dive watches. It’s listed as ‘splashproof’ in the Casio documentation which means good for a rainshower or handwashing, but nothing beyond that. Anecdotally it will survive some depth, but given its internal build, won’t do so for that long.
Usually when things fail underwater it’s due to pressure. The pressure of the water outside will very quickly exceed the atmospheric pressure inside a device and lead to an ingress of water. Dive watches, like dive equipment, use threaded seals and o-rings to ensure this doesn’t happen until you hit 2-300m or even deeper. So how to get a cheap, basic, plastic watch like the F-91W to survive repeated exposure to the deep…? Easy, just replace all the air inside it with something that won’t compress when exposed to pressure. Something like mineral or silicon oil (Silicon as the mineral, not silicone as in the tits). A light, clear mineral oil will also not affect the electronics inside the watch, especially with a digital which has no moving parts, the non conductive oil will mean electricity keeps going where it’s supposed to and nothing slows down.
The process is fiddly, but fairly straightforward. Use a watch screwdriver to remove the back of the watch and soak both pieces in the mineral oil. Gently agitate to remove any bubbles. Once convinced there are no air bubbles, the hard part is assembling under the oil to ensure everything stays together. Screw the back on, ensure the simple o-ring inside is still in position. Remove from oil, wipe everything down and leave it for a few days to check no leaks and no air bubbles. I’ve done two versions - one, I suspect, got returned to the sea at some point sadly. The other I’ve mounted on a 3d printed PETG mount so it can more easily be bungy’ed to my kit. So far it’s survived a couple of >40m dives and some shallow quarry stuff. In theory, this watch should maintain itself down to a considerable depth.
On Dive watches.
On Dive watches.
One of my few (lol) kit obsessive tendencies is for dive watches. For other divers its torches, for some its masks (wait I have that one too), for me after my general diving kit, its watches. I like a nice watch, be it a dive watch or a dress watch.
A Shearwater Petrel with cable for a rebreather like the SF2 is around £1400 at the time of writing. So two of those will be £2800 which is still considerably less than £3680 which is the current price of the Tudor Pelgos FXD allegedly used by the French Marine Nationale.
You can get a nice Doxa as a dive watch with a very nice pedigree for a little bit more or around the same price as one Shearwater, but of course it only tells the time and doesn’t do GF calculations, gas tracking, decompression maths or anything else you can do with a decent dive computer, most can also tell the time.
Therein, as the bard tells us, lies the rub. The fact I can buy a very sexy dive watch that looks nice and tells the time but otherwise is fairly useless when compared to a dive computer that’s certified to the same depth seems to render the watch a bit pointless.
So why do I love dive watches? Firstly it’s simply the only piece of male jewellery I can tolerate and I’ve worn a watch since I was a child so I miss not having one on my wrist. For dive watches specifically, it harkens back to an earlier time. When true underwater pioneers had to rely on a timepiece to track air and decompression. The sense too of owning a beautiful item that is itself a tool and able to tolerate the very extremes of places I’m ever likely to go and far beyond. I will shortly be able to dive to 60m (legally) and to have a piece of kit that can go to 10 or even 100 times that amount and withstand the pressure and still function is rather remarkable. Which is great for me - but still doesn’t explain why MN get Tudors! Incidentally the only watch in my collection I’ve ever dived with is the $50 (or £50 basically) Casio ‘Duro’ the nato strap on which was nearly the same cost as the watch.
I have recently managed to get a Scurfa MS25 (the 2025 limited edition dive watch). I also own the MS24. These British micro-brand dive watches have their own developing dive pedigree as the company is owned and run by a working saturation diver. So when people moan about watches (Omega I’m looking at you) having a Helium escape valve - this guy actually needs one. I was intending to take a sexy photo of the MS25 at 40+ m on a wreck… but see my previous post, so that will have to wait.
Fffffffuuuucccckkkks sake! Supposed to be diving this weekend. Instead was awake in agony last night, and today I’m lighter by 1 wisdom tooth and quite a few £ thanks to my nice private dentist. Hopefully less pain but no diving. (Possibly less wisdom).
The P555
The P555
Had this booked for a while, but a nice midweek dive was just what the Dr ordered at the moment. Having first managed to silence my work anxiety and lose 30bar of trimix to a leaky inflator (fixed) I was off down the south coast for the day. Fortunately the M5 was kind to me and I arrived early to park up, sit in my car and question the decision to do this in a day, especially at the moment.
Loaded my gear onto the boat, seat outside the head. Thanks for that skipper - put the CCR divers there out the fucking way I guess. Surprising to see mostly twinset/ADP divers on this boat. At just touching 40m this would normally be a CCR dive - my last trip to the coast was mostly CCRs on a 30 odd metre sports diver wreck so who knows. Clearly all regular divers though. Usual smattering of BSAC and randoms. Got to love the several people who talked to me about how sexy my kit (the SF2) was. Buy one - join me!
The wreck is a sunken submarine and I like a sub. I’m slowly working my way down the list of the ones off the UK coast and this was a new one for me. Located just past Portland bill I was happy that although there was some current running, the waves and heat were both reasonably favourable. Jump, swim to the shot and down I go. The current is high but not unmanageable - stop at 5ish m and check (with my 3d printed mirror) that all is ok. Pressures good, cells reading 1.3 - down we go. Goes f’ing dark at around 30m so carry on to 40 and see something in front of me. The shot was roughly aft of the conning tower (although in the darkness I didn’t know that at the time) I went against the current, best I could tell, starting deep and spotting conger eels living in the open cracks of the wreck. Making my way further aft to eventually the fins and rudder. Tons of sea life on her -from the congers to schools of fish and spider crabs on the hull.
From the rear I make my way down the port side (which is slightly calmer current wise) -again spotting congers but rising up a little to go along the deck. Trying to pick out features fairly unsuccessfully until the periscope housing (the larger of the two) and the rear of the conning tower. A decent poke around the conning tower but keeping my depth reasonable. Then continuing to the bow of the boat to the forward hatch and the bow. I should probably have spent longer here in all honesty but deco was ticking up. Rising back up onto the deck and back to the conning tower for another poke around. By now I’m looking at 17 or so minutes deco starting at 12m on my 45/75 GF. I decide that’s enough for today, kick off the wreck and deploy my dSMB. Text book ascent up to 18,17,16 etc, by now the 12m stop has cleared and I’m left with some at 9m. Hang there for a few minutes before making my way to 6m for about a 12minute hang. As always these things seem to go very slowly starting at what is best described as sea spunk floating by, with no reference point in the blue. All good, my handset buzzes all clear and as normal I give myself a few minutes more before slowly over the course of about 3 minutes make my way to the surface. Back on deck for coffee and a scone provided by the skipper (nice!).
All in all, a very nice dive, it’s a dark wreck and the current is well known, but both were ok the day I dived her. Fortunately the south coast wasn’t getting the 30C temperature the rest of the country was that day as well. So remained fairly comfortable on deck, suited up waiting for the jump. The 2nd dive was a drift, not tremendously exciting but a welcome addition.
Its all a bit futile.
Its all a bit futile. Don’t worry if you’re reading this, it’s not a cry for help and instead merely an observation. For a large and growing number of reasons, I’m increasingly dissatisfied with social media. Yet despite this, the desire to share interests with like minded people is surely one that is common from football fans to classic music fans and SF2 rebreather owners with an interest in British wrecks. Misery, after all, loves company. Social media is entirely at the mercy of the algorithm but this means it’s actually extremely hard to engage and share with other people beyond clicking a ‘like’. Blogging I will admit is very 2002 (happier times!) but at least it’s my own authentic voice, my own findings and areas of interest and I’m happy if someone wishes to reach out. Until then, I write for my own satisfaction and the hope that one day, someone, somewhere, googles something and the hateful AI will remember this small diving blog and throw up something that may assist another diver, 3d printer or miserable overworked person who wishes social media was actually social.
Why the SF2 (Part 1)
Why the SF2?
My rebreather experience started basically at the same time my ‘technical’ (other than nitrox if you count that) diving did. As I was starting to look more at twinsets and accelerated decompression I got to do a BSAC ‘Try Rebreather’ day at Vobster (an inland dive site) with some friends of mine.
First off I tried an AP Inspiration. I will say the lovely BSAC instructors ignored me telling them I needed X amount of weight even with a big steel twinset, so I was underweighted when I went in. This resulted in me sucking the loop empty every breath to try to control buoyancy, having the ADV fire and a horrible feeling of being near death. I essentially hated every minute of the dive.
My buddy, who is a persuasive man, then convinced me that it was all fine and I should try a Liberty CCR for a 2nd attempt. Which I did, having first become slightly poorer and BSAC slightly richer. This time my weights were more or less correct, everything functioned and I didn’t think I was going to die. Feeling like death is near was a regular experience when trying rebreathers I later got to learn. All good, I liked it but not enough to really convince me I was ready to leave my twinset and acceleration deco.
Fast forward several years, my persuasive buddy has been diving the Liberty for several years (he really liked it). I’d done a lot of decent diving on my twinset and stage including Scapa Flow, Shetland and a number of things on the south coast. I was (if I say so myself) pretty damn good at the planning and gas switching that came with diving this setup. Then… buddy and I were on a 45+m dive on the south coast, a ship that had been on my wish list for a while. Shortly after boarding, I realised I was the only non rebreather diver on the boat. Then the final humiliation came, the skipper shouted out ‘whos Belemnite?’ I put my hand up - he looked at me then the clipboard. ‘You’ve put 1 hour - is that total dive time?’ Yup, everyone else was doing at least another 30 mins, but my gas planning put me at 35 minutes or so and then the rest coming up. It was clearly time to buy a rebreather.
3D Printed SF2 loop caps
I am a menace with my 3D printer. I really wanted some loop end caps to seal my loop when I’m not using it. This comes after the last time it had been sat on my work bench for a while, I set everything up, did a pressure test and started coughing. Understanding that either my just filled scrubber had not been sealed (it was) or the counter lung was dusty (it wasn’t) then the only remaining thing was my loop. As always I’d sterilised the hell out of it and let it dry after it was last dived, but maybe dust or something else had gotten in. I washed it down again with Chemgene and all was well on the dive the next day. Hence trying to find endcaps, as no one else seemed to have done this, and I couldnt get other branded rebreather ones to fit (what mutant size is the JJ!?) I made and designed my own. Get yours at makerworld.com/en/models…
I hate when work means I’m not even thinking about diving. Can’t CCR when my head feels like its going to explode.
Problems with UK Diving (Part 1 of lots)
Every single UK based diver, skipper and dive boat owner/deckhand and dog I’ve spoken to, says the same thing. UK diving is dying off. Having just come from a days diving a sports diver level wreck on the south coast that was only dived by what you would probably class as ‘technical’ divers, I’m finding it hard to disagree for reasons below;
Problem 1.
The weather. Honestly does this need elaborating on? The weather in the UK has cost me so many dives, lots of hours at home or going to the local quarry rather than diving a tasty wreck because the wind/rain is too much. Even when I’ve made it out - I’ve seen people puking, sunburned and soaked to the skin. Basically good days diving on calm seas in mild temperatures is a UK rarity.
Problem 2.
BSAC. I’m saying it - after the weather, the issue in the UK with diving is divers… or especially the national governing body. Firstly and most fundamentally they do naff all to support divers. Over covid they failed to lobby for divers to continue (despite the fact we’re in self contained breathing apparatus) and since then, they do sweet shag all to support branches. There are a lot of hard working volunteers and instructors, and I would know, I used to be one. When things go wrong though they don’t offer any support or guidance and let branches sort it out themselves. In the case of my former club, this involved kicking out anyone who was concerned the diving site had been condemned by a chartered surveyor and allowing a convicted (bad conviction - very bad) to the club and to sit on the committee. That’s the brief version…the full version would fill a book. As a person who thinks safety is a good thing and that individuals who have seriously dodgy backgrounds probably shouldn’t be allowed around kids, I was pushed out, stabbed in the back and ostracised. BSAC…didn’t want to know.
Leaving club politics aside, there comes the ‘crabs in a bucket’ mentality and the ‘oh we don’t do that dear’ attitude. Now hardly unique to diving and pretty common in British life, but this means that the people actually diving tend to be the ones happy doing their own thing and making their own bookings. Not waiting for the branch elders to do it for them. The same is true of training, most branches seem to want you to turn up somewhere for 12 weeks in a row without missing a session, to be given variable quality training by instructors who qualified 40 years ago and haven’t really kept up with advances and to whom nitrox is still voodoo gas. This doesn’t take into account the fact people have busy lives and want to dive the same way they can abroad with nice rich mixes when needed.
For most people it’s quicker and easier to pay PADI £600 and qualify somewhere warm, then cross over to a club. The other side of this is people who DO turn up for the 12 weeks, tend to qualify whether they actually understand the material or not (mind you, this is true of PADI too). Leading to some divers who really don’t get that they might be breathing 100l a minute at 30m and just how quickly their pony tank will run out. Again I’m speaking from direct experience here. BSAC branches continued belief that a 15L and a 3L pony tank are just what you need in the dark on a British wreck is worrying.
Why a blog?
Why blog? Mostly because I’m totally sick and tired of social media and wasting time on it. If I can spunk my thoughts onto the internet it moves me away from Meta controlled BS apps and makes me write something. Getting people to actually read it on the other hand is a totally different proposition. The algorithm now dictates peoples life to such a degree that its hard to find small subgroups of people with shared interests… none the less…here I am blogging about SF2 CCR and probably some general dive stuff, 3d printing and random stuff.