The carabiner. Loved by climbers for exactly the same reason that it's gained the nickname of 'suicide clip' in diving circles. See, carabiners work by maintaining their locking capabilities while under tension, like when a climber falls off a rock.
Problem for us divers though, is that what happens if we get entangled in some kelp, or fishing line, or wreck / cave line or the mooring line or any one of dozens of other things we can get tangled in underwater? That's right, that carabiner keeps us locked in, unable to release the tension and get ourselves free...
Solve this problem with a simple stainless steel double ender snap. These snaps are designed to be released using the external 'lever' meaning that, even if you're tangled and under tension, you can still open the clip.