Try telling that to a customer of mine who got hosed by them....

Again, READ THE FINE PRINT....
He had a failure due to
lack of maintenance and they would not cover it, not unusual in most policies, but they also would not cover salvage or environmental damages something most
reputable marine insurers do and will..!! It all comes down to the fine print. He not only lost his vessel but then got sued for clean up!
I am not sure if what you say is true.
I keep my boat at a state of Hawaii boat harbor and the state recently required us to raise our liability (including salvage and coral reef damage) from $300k to $500k.
http://files.hawaii.gov/dlnr/dobor/notices/Notice-Boaters-201307.pdf
From above:
"Beginning January 1, 2014, all applications for renewal of mooring permits must
be accompanied by proof of insurance with a minimum of $500,000 in boat
liability coverage (protection and indemnity) that names the State of Hawaii,
Division of Boating and Ocean Recreation as “additional insured" or "additional
interest.” AS A REMINDER: the insurance policy must also cover salvage costs for grounded and sunken vessels, damage to docks, pollution containment, wreck removals, etc. Proof of this coverage must be stated on your policy declaration page."
My broker deals with Progressive as well as others and Progressive does cover the above requirement and the state reviewed my policy to insure it did. Also, I spoke with a Progressive rep after the Japanese Tsunami sunk a lot of boats at the dock and she assured me Progressive paid for the loss of the boats (me- I went to sea and returned to a damaged dock).