Maybe there's something new out there, but I've never seen a "trip insurance" policy that would cover the loss of an underwater camera while on a dive...
Insurance such as D.E.P.P. that covers camera equipment loss, theft, flooding, damage, etc. is what you would need. We've got our photo and video cameras, housings, strobes, as well as all our dive gear that we travel with on a D.E.P.P policy. It won't get your photos or video back, but it sure makes the cost of replacing and repairing equipment easier to live with.
Sure, DEPP would be the preferred coverage, but I figured if he had that then these two threads wouldn't even exist. Some would suggest a homeowners insurance claim; I could offer reasons why I wouldn't but will skip that for now. Since we don't know if Tundra_Trog had trip insurance, this is hypothetical - but since you asked, I'll give it a shot...
Of the various reasons I always take low cost trip insurance on international trips, loss by airline (with a $907 or $1250 liability limit for international), porter or driver outside the U.S.
are covered in "Baggage and Personal Effects $2,500" coverage. It's not as easy as the consumer might prefer, as the insurance company cannot be easy on
"I dropped it so you pay for it" claims, but I'd certainly try for it. I did phone Travelsafe to discuss the likelihood of payments in case I missed something in reading over their provisions, and yep there's coverage - just not as easy to justify as it would be if someone else lost your property. Required:
"In case of loss, theft or damage to Baggage and Personal Effects, you must: 1) immediately report the incident to the appropriate local authorities (i.e. local police or other local government authorities) and obtain a written report to include the value and description of the property loss; and/or 2) report the loss to any responsible party (i.e. hotel manager, tour guide or representative, airline, cruise line, bus line or other transport official), and obtain a written report of the loss to include the value and description of the property. We will not pay for further damage if you fail to take reasonable steps to protect your Baggage after a loss." Then there is a $500 maximum payment that can be justified; $500 will not replace this loss, and DEPP would be preferable, but $500 would help.
Do I know anyone who has filed a claim for an item they dropped & lost on a trip? Nope, so far the answer I get to my question has been
"No, we didn't buy trip insurance." The two claims I have filed on trip insurance were both paid in full, but they were for trip interruption & delay.
I keep looking at the coil strap you suggested and asking myself if I want to mess with that in addition to everything else I hang off of my BC. Looks like a very good idea.
I wrote on my housing and camera with paint sticks: tacky looking but accomplishes what I wanted. 
