"Historically, it was known by the Romans as Palus and later by the Moors as Al Buhayrat Al Qsarand. In the 17th century its name changed to Mar Chico, meaning "small sea" and later as El Mar Menor. Originally, it was a bay opening into the Mediterranean; at either end, volcanic reefs gradually held back the sand and sediment that was dragged along by the sea currents to form a sandy column of dunes and rock vegetation and long beaches in contact with two seas. La Manga sandbar is cut off by natural channels that keep the two seas in contact with each other; the so-called golas allow water from the Mediterranean into the lake. As such, the space was untouched until the 1960s, when La Manga was discovered as a tourist resort and underwent a transformation which included the urbanisation of the area and the construction of tourist infrastructures." (Source: wikipedia) More info: here, official tourist website.
From this side, La Manga and Mar Menor looks like a beach at the Caribbean Sea. I commented at some previous posts that Mar Menor is the perfect place to practice sea sports.