We did the 3 hour snorkelling tour from Almirida. It was an amazing experience. We had the boat to ourselves (5 of us - 2 adults, 3 teens). Freya, our guide, was great. We went to three sites, each was very different - and all were full of fish and other things to see. It was very professionally run and you got absolute maximum time for snorkelling. I would thoroughly recommend them for an unforgettable experience. (They also take underwater pictures which are emailed to you very quickly afterwards.