The illegal bottom paints are still available on the Internet!

They are so poisonous that they were banned from the Earth's oceans
worldwide, 'cause it was killing everything that came close to it!
Since Wolfeboro (at least) is contemplating drawing water from Lake Winnipesaukee for its new Town water supply,
old bottom paints (especially) are going to be
very suspect in Winnipesaukee in the future!
Otherwise, I agree with XCR-700's advice—sand it down to the original gelcoat. To be on the safest side of this issue, I'd wear the most protective safety-gear possible when removing any bottom paint anyway.
(And do it
outdoors—in Massachusetts

).
Me, personally? I'd try a test-spot
above the waterline using a liquid remover—first.
On sailboats, leaving the bottom a little bit rough (with 400-grit-waterproof) doesn't seem to hurt anything

seemingly, there's some advantage in carrying a micro-thin layer of H
20 along with you.