You'll probably need multiple policies, although you should be able to get them done through a single
broker. The policies will (probably) be placed through different carriers.
I don't know if you calculated this in, and it depends on where you're going, but here on the west coast
want you to have liability insurance and name the marina as additional insured. You might want to check on that for any marinas
you're planning on staying in, if any.
More broadly though, a good maritime insurance agent should be able to point you in the right direction. I know a guy in California
who's great, but insurance is licensed state by state here in the USA.