2 month bump or so, but to answer your question with my opinion i think it would be best to..
get the surf mount, mount it to your kayak. the surf mount not only mounts the gopro, but it also includes a string attachment in case the mount fails. to add even more safety, i would go as far as to thread my own safety string through the mount and attach it elsewhere, just so if it does fall off, you have a safety line.
i plan on cliff jumping this week with mine, and im just going to thread a string through where it mounts to gopro mounts, and tie that around my wrist, then take a small ring from a pool noodle and thread that through there to. so if it comes off my wrist, it floats.