I like using gorilla glue. LOL. I had good luck dumping some epoxy in the toe of some fins I had that were too big when I was younger. After it set, it made the fin a bit smaller, and I was able to dig it out when I actually grew a *****. I mean feet.
Snapped one of my tethers down in Bocas..haha but that was a really heavy wave. No joke, chased my churchill for almost a mile down the beach until I was able pounce on it! It kept getting sucked under and would appear way down the beach again. Just as I was about to give up, I saw it and was able to get it! But, tethers have saved my fins MANY more times than my tether snapping.