I learned in my Recreation Law class in school that waivers for private trips can actually create more liability. I tried telling Robin at the Mishawaka this once, but he just stared into space and grumbled something about bad mushrooms.
As long as you aren't charging a fee to take your friends down the river, you aren't doing anything criminal by floating navigable waterways, even if you suck and are in way over your head. However, you can sue for anything in America, provided you can demonstrate damages. That is where personal liability insurance comes in to the situation. Even if you're totally free of civil blame, it's nice to have someone foot the bill for your attorney. This type of insurance is rolled into many property insurance plans. You should read yours carefully to make sure you are covered.
My dog was a 60 pound husky named Disco. He wasted that Alpaca, which was named Braveheart. My dog actually came back home a week later and lived for years to tell the tale. That was the first time someone pointed a shotgun at me...