There are 20 new mooring balls at Staniel Cay in front of the Thunderball Grotto. They are on a first-come-first-served basis. No reservations required. $40/d.
Call Staniel Cay Yacht Club on VHF 16 or email firstname.lastname@example.org to inform them that you are taking one. Give credit card over phone/email or take the short ride to shore to check in and have a drink at the same time.