Parachute cord lanyards are standard, but they tangle like crazy in current. What about using retractable keychain reels? They're cheap, lock in place, and won't wrap around your arm. You can clip them to your belt or harness so when you drop a tool, it just hangs there instead of sinking. I've seen divers modify them with carabiners for quick release. Sure, they might not hold up to heavy abuse, but for wrenches and such, they work fine. It's a dumb simple fix that most people overlook because it's not 'professional gear'.

That's the best kind of family history to find out.