My personal liability umbrella policy requires that I have $300,000 in primary coverage under a marine
policy. After that the umbrella picks up. So that doesn't sound like an option for you.
But there are liability only marine
policies. Talk to a marine insurance
broker. Al Golden of IMIS in Grasonville, Md is one. Jack Martin of Jack Martin Associates in Annapolis
, Md is another. Either should be able to get you a marine liability only policy with coverage anywhere in the world.