Mar Menor

The Mar Menor is a lagoon of about 135 square kilometres separated from the Mediterranean by La Manga, a sand bar twenty-two kilometres long and in places only a hundred metres wide, connected by narrow channels. Its shallow water, averaging under four metres, warms early and stays warm, and the salinity is higher than the sea, which made it a resort destination and gave the mud on its shores a therapeutic reputation. It is also in crisis: decades of nitrate runoff from intensive irrigated agriculture in the Campo de Cartagena have caused repeated eutrophication events, including mass fish deaths in 2016, 2019 and 2021. In 2022 Spain granted the lagoon legal personhood, the first ecosystem in Europe to receive it, following a citizens' initiative.

What you actually see

• The shallow warm water - a lagoon averaging under four metres deep.
• La Manga - a twenty-two-kilometre sand bar with sea on both sides.
• The mud baths - therapeutic mud used along the northern shores.
• The ecological crisis - visible algae and the effects of nitrate pollution.

When to go

May, June, September and October; the water warms early and stays swimmable late. Summer brings heavy Spanish holiday crowds to La Manga. Algal events are unpredictable and can make the water unpleasant or unsafe.

Honest expectations

The lagoon's condition varies and can be poor, with green water, algae and warnings; checking recent local reports before planning to swim is genuinely worthwhile. La Manga is intensively built up with high-rise blocks. The crisis is unresolved.

Nearby

San Pedro del Pinatar's salt lagoons lie north; Cartagena and Cabo de Palos are south.