Visit Blue Lagoon Malta

This is actually not at the main island of Malta, but at the smaller island of Comino just north west of Malta. It is very easy to take a boat from the harbour to get here with a tour. The water here is among the clearest in the world. Bring snacks and water there is limited shops at the beach.

Blue Grotto

If you are in Malta this is a must. You take a boat ride with a tour inside these amazing caves with the bluest water ever.