Re: What sailing knife do you use?
I have a Myerchin Lightknife. The marlinspike isn't a spike exactly, but a slim hook that you can push into a knot, hook below the loop holding it tight, and remove it pretty quickly. The serrated blade cuts nicely, but the tip is pointed and might hole anything inflatable (which hasn't been an issue for me yet).
It's got a 18" lanyard attached to a small carabiner that i clip to a belt loop. The knife is in my pocket, easily retrieveable with one hand, and won't go for a swim.