My next question is about swimming fur bearers. Reading over some of the posts and looking at pictures plus the gist of the trappers ed class it seems usually the traps are completely underwater. Sometimes in a drainage I have seen the water wasn't deep enough so the top of the trap is exposed. Does it matter that much? Also does anyone set the traps for these critters on the banks or runs that are on land not in the water?
Most of the time you can find a water set and there are significant advantages like Lewy mentioned, 3 day check. I find water animals easier to take care of if they cool out in water and besides that they can beat themselves up and test your trap if they are alive in it.
Also it can be easier to get one under water depending on species. Otter can shy from a trap at times but don't seem to notice the trap as readily when it is underwater.
If the water is a little shallow to get the trap underwater I use my Pulaski to deepen it a bit.