What comes to mind when you think about the word "lagoon"? If you're thinking of a watery sanctum, you're on the right track. If you're picturing a mosquito-infested bog, I can give you something to help with that sad mental image.
Behold the lagoons of the island Comino.
Comino is the tiny island between the greater island of Malta and its little brother, the island of Gozo. All of these islands belong to Malta proper (which is its own country, if you need a geography bump). You can traverse the entire island of Comino on foot, in a day.