St Martin is a small island with a big charter market: two countries, two currencies, a busy international airport and one of the Caribbean's main cruise ports. Plenty of guests only decide on a boat day once they have landed, and they book whoever answers first.
booksea puts a booking widget on your own website so that answer is instant. Guests pick a trip, a date and a boat, pay a deposit, and the booking goes straight into your Google Calendar, whether you run snorkel trips out of Simpson Bay or crossings to St Barths from Marigot.
There is no marketplace between you and your guests and no monthly fee on Pay-As-You-Go: you pay 3% when a booking comes in, and nothing through the quiet months of hurricane season.