While standing on the concrete jetty I could see a shoal of thin fish with long pointed jaws in the water below. They were Keeltail Needlefish Platybelone argalus. They are in the Family Belonidae and are found only in the West Atlantic. They grow up to about 0.5m but these were maybe half that size. They are related to the Garfish that we get here in the UK. Confusingly Garfish in the United States refers only to similar looking fish that belong to a different Family altogether that are found only in freshwater.
I wasn't feeling great this morning so decided to stay around the hotel not far from a toilet while the others went off and saw and photographed Dusky Swallowtail, Neleis Sulphur, Cuban White and Cuban Flasher. Bit miffed by missing the latter!