Boat insurance for your boat, is basically identical to auto insurance for your car/SUV.
You start with Liability Insurance to others, both Bodily Injury and Property Damage. The big difference is that Boat Liability is much cheaper, meaning that most people buy higher limits.
Medical Payments on a Boat Policy, is the same as Medical Payments on an Auto Policy, it pays up to the limit purchased for medical bills caused by someone on your boat getting injured on your boat.
Uninsured Boaters, is essentially the same as Uninsured Motorist. Again, because it is cheaper, most people buy higher limits.
Coverage for the boat itself is based on the value of the boat and its trailer, if one exists. Opposite of an Auto Policy, on Boat Policies Collision is Cheaper than Comprehensive, since boats are stolen at a far greater amount than get into an accident damaging the boat.
Boats, and their trailers are covered for accidents on the street, as well as in the water.
Towing a boat is a lot more expensive than towing a car on the water. Most people procure at least $300 of in water towing.
More like a Motor Home, Boats also allow for insuring personal items kept on the boat like portable VHF radios, towels, clothing, etc AND Separately Fishing Equipment. Both are extra cost OPTIONAL coverages.
Most boat policies limit you to inland lakes or rivers AND no more than 75 miles on the ocean from your home port, without you paying extra.
Most policies give credit if you have taken either the Coast Guard or Power Squadron Courses.