Full-day (8-hour) diving trips operate from Reykjavik all year round. The price includes two guided dives, pick up from your accommodation, all equipment, and some snacks. You’ll need a minimum PADI Open Water qualification to dive. There’s also a family-friendly snorkelling version available from May-August, which lasts 4-8 hours, so non-divers can go with divers. Diving and snorkelling are in dry suits; the water is a glacial 2-4 degrees Centigrade, even in summer. Take warm clothes with you and thick socks.