It depends on the company and destination. Paddle boards, kayaks, fishing gear, waterskis, fast speed boats, drones etc are all available at an additional price. However, snorkels and fins are typically included in the charter fee and on board already.
I have used Hinde and Kitch on three occasions now and they have never disappointed. They go above and beyond to help with whatever is needed. Their guidance and professionalism is unparalleled, finding the perfect boat for our group and suggesting three fantastic spots for our holidays. We even got a yacht upgrade last year!