A point of comparison. I recently got quotes from Progressive. No line item for environmental cleanup / spills. When I asked, they said that was included in the liability limits. You'll notice on a Boat US policy, that item is a separate line with very high limits. That's one of the reasons I stick with Boat US and have also not found similar coverage from anyone else for the same price.
Don't trust that. They are leaving you hanging out in the wind. Leaving you to arraign contractors and make payments. That is what you are paying the insurance company to do. let them deal with the salvage and clean up rather than you paying and hoping to get reimbursed enough to cover what you paid. Allstate is the other company that folks have had issues with. The other thing that happens particularly after a storm they will send adjusters who know little or nothing about boats. Have a friend who just went through this with his Hobie one of the newer rotomolded ones. The adjuster wanted to give him a check for a couple of hundred dollars to have it "refiberglassed". Documentation from a dealer saying the hull needed to be replaced and that it was not a fiberglass boat did not sway the adjuster. Finally got an adjuster who knew a bit more and got it resolved.