There are many points where a secure attachment is required between two pieces of gear, that can also be quickly/easily disengaged; speargun to float line, float line to float/board/kayak, stringer to float etc. I've experimented with many clips and have come to the conclusion that without exception, all available clips that can be quickly opened are not reliable.
One time I was diving with a kayak attached to a float line attached to my gun, using a clip that I thought was secure. At some point I felt very little drag and looked back at the kayak, it was gone. If you think you'll always feel/know when a piece of gear comes loose, and be able to recover it immediately, you're mistaken. In my situation there was a strong current and by the time I noticed the kayak was gone, it has floated off about 150 yards. I started to swim hard after it, but couldn't make headway as I was still holding the gun. I even tied the float line to my belt so I could tow the gun and use both my arms to swim, but realized that I will never catch the kayak. Fortunately I saw that it was moving at an angle that would eventually bring it to the beach. So I swam straight for shore. I was doing my best to swim and not lose sight of the kayak. When I reached the shore I had to walk 1.5 miles up the beach to get to the point where the kayak came close enough that I could go out and grab it. It would've been an expensive lesson, a Scupper pro with a paddle, sonar, and other gear on board.
Since that time I decided to never use a clip that had a chance of opening on its own. You'd think that some clips have little chance of that happening. But I guarantee that eventually there will come a moment, when all the stars are aligned/the right combination of movement of the gear due to current, waves or whatever will open the clip. You'll then be left wondering, maybe I didn't close the clip properly? You'll never know the answer except coming to the realization that there exists the possibility of it opening on its own.
One of the things that prompted me to post this is Reefchief's recent adventure with the Banks board http://spearfishing.world/80934-post247.html. Basically what happened was that a Tuna clip, which some tout as being very secure, opened and the Banks board with an iPhone in it and a bunch of other gear floated away and was gone out of sight before Mark became aware of the situation. It would've been an approx $800 loss had the iPhone not been left on the board TURNED ON and we could GPS track it with another iPhone and eventually make a recovery with a boat.
For a long time the only secure option I had to use for a quick disconnect clip was a stainless steel quick link. These are readily available at Home depot in different sizes, are not expensive, and very secure. The problem with them is that even though they're stainless steel, the threading accumulates corrosion fairly quickly, and the nut becomes too difficult to unscrew with only finger pressure. So you have to keep buying them every couple of months. Also they're not as quick to open as I'd like, because often you're not sure which way the nut needs to be turned to open, and end up tightening it first and spending some time figuring out whether you're unintentionally tightening it or if it's seized.
A couple of years ago I found the ideal solution, a quick release stainless steel snap, with a screw lock. An added advantage is the ring retainer that will keep one of the pieces of gear fixed at the end of the clip, and will not chafe rope. The size that we need is hard to find, and they're relatively expensive. Guys that saw me use this clip would often ask where they could get it. Recently I've been able to source some good quality snaps and I'm happy to make them available Freedive Store - Locking Stainless Steel Snap.
