insure via your homeowner's policy. It is not implied. call your agent.
A separate rider is necessary. For each craft you supply the boat model, make,year and HIN and its replacement cost.
It will insure your boat in your home, in the yard, on the car, or even in storage.
You can insure for replacement value of your boats and gear (paddles, drysuit, etc). There is also an allowance for towing and salvage.
My cost to insure two composite seakayaks and gear is $72 per year. YMMV based on area and claim history.