[spaghetti]

I too often hunt in a murky water lake, where I mostly use a 75 centimeters: when I say "murky" I mean murky, so a 90cm would be too long cause I couldnt' see the spear tip of it. You must consider the length of your arm, of the barrell and of the spear: as a result, if visibility is about 3 meters, you CAN'T hunt with any gun longer than 75.
The Cayman is better then the Excalibur, but on such a short one the difference does not matter so much.
So assuming the Excalibur to be a little cheaper, go get it: it's perfect for lake hunting and will make you save those few bucks.