Depends where you are.
I think that all marinas here in Florida require that you have liability insurance - and require that you name the marina as a loss payee. The amount of liability insurance they require depends on the marina. We have a policy on our 40' boat through Zurich with $350k liability and $150k hull/replacement value. We pay $3k year. Boat US is really high right now in Florida.
BTW, if you don't plan to get insurance, I hope that you don't ever dock or anchor near my boat. I have seen many hurricane boats here that caused damage to other boats, or just sank and were abandoned. No insurance, so the owners just take off and leave everyone else to take care of their problem.
LaLeLu 40' Caliber
Merritt Island, FL