The most famous dives on Saint Helena are the two wrecks found off the mainland. Papanui, the wreck of a coal ship, is located in shallow water. Dark Dale was sunk during WWII and you have an excellent shot of running across large pelagics like tuna and grouper. Sometimes whale sharks even make an appearance - an unbelievable bonus.
Around Saint Helena there are plenty of small islands to see. Thompson’s Valley Island has spellbinding volcanic caves, carved thousands of years ago. Strange creatures reside in the caves, making for some interesting sightings.
You can expect warm, mild temperatures throughout the year, as well as exceptional visibility. Rain makes quite an appearance in June and July but is also when sites are quietest.