Such a phenomenon can be seen each year in the bay ofBalaklava under Sevastopol: all its water area gets filled with jellyfish.
Boats, ships, expensive yachts stand in the white jelly messsquishing under the feet of people walking by.
According to scientists this phenomenon occurs due to windcurrents and population inflow - jellyfish accumulates in the water area of theBalaklava bay like in a sack.
Another side factor is high temperature of both the air (to+20C) and the water (to +14C) in this period.
Thanks to aquatek-filips for the photos!