There are legitimate and dependable boat transport companies with their own fleets of vehicles and decades of experience. They are not the cheapest, just the ones you can trust.
On insurance, don't depend on them to have coverage, make sure there's a policy in effect covering you. Even if you have to duplicate coverage. It's not all that expensive to have an addendum put on your policy to cover it during the transport.
Boat transport is a very specialized area of trucking and when done by companies that are only in that business, nothing like the general trucking industry.