A jellyfish “plague” in a Black Sea bay in Ukraine has ruined swimming season for local residents.

Swarms of jellyfish have swept along the coastline in Balaclava bay near the Ukrainian port of Sevastopol.

The same thing happened in the summer of 2012, but locals say they have never seen so many jellyfish before.

Lots of people normally go swimming at this time of year but they have not been able to because the layer of jellyfish is so thick.

Only fishermen are happy with the plague.

Sea bass hunt jellyfish and that means there has been lots of sea bass around to catch.

Marine biologists expect the jellyfish to leave the bay when the wind changes direction.