Modro oko, Protected lake in Dubrovnik-Neretva County, Croatia

Modro oko is a small lake in a partially submerged karst depression on the right bank of the Neretva, between Desne, Banja and Komin. It lies at sea level, reaches 18.3 m deep, and is linked to Lake Desne by a 350 m long, 3.5 m wide channel. Its brackish to salt water appears intensely blue because of the white limestone of the depression.

The lake system developed through natural geological processes in the lower Neretva region where Croatia and Bosnia Herzegovina meet. The formation took shape over millennia through the interaction of water and limestone geology.

The name Modro oko means "blue eye" in Croatian, referring to the intense blue colour the water takes from the white limestone of the sinkhole. The lake and the neighbouring Desne lake were declared a special ornithological reserve by a Croatian government decree of 20 August 2020, and the surrounding reedbeds are noted for their diversity of marsh birds.

The best time to visit is during the dry season when water levels are lower and access around the site is easier. Wear comfortable shoes and bring sun protection, as the area is open with limited shade.

The lake sits in a sinkhole at sea level and reaches a depth of 18.3 m, while a channel only 350 m long and 3.5 m wide links it to Lake Desne. Its water is brackish to salty, and the white limestone of the sinkhole makes it appear intensely blue.