Hello from a fellow New Englander!
Although you're building a base tan, I'd still go for a sunscreen with a SPF of at least 30. (Penny, I'll have to try the one you recommended.) When out of the water, cover up as much as possible. And don't forget areas like behind your knees and the tops of your feet. (Learned that one the hard way.)
Also, bring a lotion with aloe so that you can soothe your skin once back in the cabin.