Make sure you seal up any cracks/holes, it's a bad feeling when you're going across water and you belt starts slipping 1/2 way across. If you're doing it in the winter/spring its better if you can find a spot thats flooded vs. open water....alot easier to get out if you happen to sink it.
I sunk my sled in open water , my belt got wet and i ended up sinking 10ft from the edge of the ice lol. It was in about 10ft of water and just so happened that it settled on the bottom with a big rock between the skis, we didnt have any rope so we had to go and get some then I cut down a tree and stuck a loop of rope on the end of it, layed down on the edge of the ice and reached down to the bottom and pushed the rope through the bumper and pulled it back up again, it was pretty difficult and If i couldnt get that to work I was going to strip down to my boxers and swim down to tie on the rope. After fighting with it trying to drag it up over the rock between the skis we finally got it up and got it fired up, thought all was good but she locked up on me the way home......the sled was on the bottom for a couple hours and the infamous leaky oil cap and let in some water and starved it from getting oil. That was almost 10 yrs ago and I was new to working on sleds so it didn't even cross my mind that there could be waterin the oil.... so if you do sink make sure no water has gotten in your oil or it's gonna cost you alot of $$$.
I don't really play around with it much anymore just usually if i have to cross water, I don't go out of my way looking for water to cross, even though I had another close call last year on a fairly short stretch of water, took out my swaybar and forgot to cover up those nickle sized holes for the swaybar brackets (one is right in front of the clutch).
If you seal it up good you shouldn't have any problems, I knew a guy that had an old v-max 700 that could go on water until it ran out of gas (everyone knows hot easily the yamaha's got wet on water) He put a light inside the hood in the dark and sealed up everywhere any light shined through with marine silicone.