Looks like abraded
gelcoat. Might be no primer was used.
If it's a polyester boat, it's a good moment to add an
epoxy barrier coat to it.
Scrape all antifouling meticulously off, apply two layers of barrier coat (ideally different colors so you do not miss spots.).
Apply your new antifouling.
Good luck, scraping is hard
work, I did it last year on 30m2 of our cat