Transport to the island can be either by plane or bus+ferry. Flights are only from Havana (to Nueva Gerona), & you need to book well in advance.
Even the adventurous types will prefer the plane to the bus+ferry, since the ferry is a catamaran with no open-air deck.
Book Scuba Diving Classes & Sessions (link opens a new tab)
Please note the diving sites are only accessable by boat. The boat & crew hire for the whole day is included with dive packages.