If you want to hunt them sit along the water on a moonlit night and they are very easy to see swimming around. They are much more active at night than in the day. Look for areas on the bank where they are chewing on trees and there should also be fresh "slides" where they are exiting and entering the water. When you find an area with recent activity sit and wait. They are very good at seeing movement so be careful. It doesn't matter what you shoot them with, they sink fairly fast after being shot. If you want the pelts you need to shoot them on the bank, otherwise they will sink never to be seen again. They are a very passive animal, don't worry about them attacking you.