Your homeowner policy will generally not be acceptable to either banks or marinas. Boat insurance is designed to address the specific needs of boaters.

Most boat policies provide coverage for a broad array of calamities including theft, vandalism, lightning, fire, grounding or sinking.

You can choose to protect personal items such as water-sports equipment and fishing gear as well as provide towing coverage.

You won’t be able to get a loan on your boat without providing the bank with proof of insurance that covers the full value of the boat in the event of a loss. The bank gets listed as the lien holder on the policy so that if any loss payments are made they’ll be listed as a co-payee on the check.
Most marinas require proof of liability insurance before they will accept a contract for a slip or a mooring and some will want to be listed as an additional insured on the policy.

A collision with a small powerboat can cause serious injuries, and even if you are not found liable for those injuries, you could end up spending a significant amount of money in legal fees to defend yourself.