When I did mine, it was to Inon z240s and I had to mount a fiberoptic cable at the top ball fitting to get the light from my little LED flash to the strobe sensor (on one - the second strobe triggered from the first just fine). My very first dive with it, this failed because I (in hindsight, stupidly) used a fairly fat (like 3mm dia) "lightpipe" fiberoptic which was just plain brittle. First time it got wrapped around the strobe arm it snapped. A friend has had a set I made for his Nikon and hasn't told me it did the same for him, but it's been years since we've talked about that specifically. Fortunately I took an Ike to Inon manual sync cord as a backup and off we went for the rest of the trip.
With all the talk of failing electrical sync, I've never had one fail. Of course I've also only been on say 5 actual photo dive trips in 6 years but I'd almost expect the 'infrequent idiot' dive photographer to be worse off than the near-pros, proportionally. Guess I'm not factoring in opportunity multiplier enough.
BTW I never marketed my LED flash because a) it's a battery, a single switching MOSFET, a couple resistors, and an LED - I mean, you should be ashamed to buy one, frankly.
. (Hedwig made a much more fancy circuit but for manual flash triggering it's really unnecessary.) But b) at least for my hand-drawn circuit board and mounting it really was going to be a unique shape for every camera to fit the housing bump. I did one for my Sony A55, one for a Nikon (D90? I really don't recall at this point) and realized I just didn't have the wherewithal to plan and manage configurations to offer it for people.
That, and in my case - A55, electronic viewfinder first generation with no 'setting effect' menu option to prevent viewfinder darkening if the camera doesn't know a strobe is attached and settings seem underexposed - manual sync just wasn't a viable solution after all. My more recent cheap TOSlink cable adaptor to get light from an electrical sync-ed, TTL-triggered DS51 to my Inons would also likely let me mount the fiberoptic signal from my in-housing LED to the Inon without the breakage problem I had years ago - but I'd be back to manual sync and shooting blindly. I'll hold out that idea for an upgrade perhaps though since all newer Sonys have the menu option to prevent the EVF blackout (except Ike just went opaque with their housings....hmmm.....)
As much as I like the Inons for reduced bulk compared to the DS125-161 strobes, I have to admit I remain an Ikelite 'fanboy'. Their price for a housing with TTL circuitry is 3/5ths anyone else's equivalent housing without it. As poor as some of my camera choices may have been over the years (Oly 4:3rds E330 to Sony A55)..I'd never have shot underwater at all if it weren't for Ike. I'm not poor by any means and even sprung for a full frame A99 as my last (not underwater) body upgrade during something of a non-diving spell but $1200-1500 vs. $2500 or more for a housing remains a huge motivator for me. I admit I wish they'd come up with the electrical sync (with TTL connectivity) to light-output technique themselves (basically everything in the DS51 minus a big flash tube), but I don't really know the business metrics. Would that option, at say $150-200, let them sell more housings to people who wanted Inon or other strobes? Or would that cannibalize more potential DS strobe sales than it gained them in housing sales? The fact the Manta never came out tells me housing sales is the more important factor, but I could be wrong....
I've also never understood wanting to disconnect/reconnect a strobe underwater. The ONE time it would have been useful to me was with a Y cable when the 'primary' strobe (powering the TTL circuitry) lost battery before the secondary....if I could have swapped them I might've gotten another shot or two. Not exactly a game changer. I guess if you want to abandon your strobes or hand to a buddy to trigger optically from another angle (like with the Triggerfish) you can disconnect/ reconnect FO, but as long as I'm only electrically triggering one and the 2nd is optically slaved, I can still do that to a certain degree as well. (Not that I've ever tried.)