A massive jellyfish invasion clogged the cooling intake systems at France’s Gravelines Nuclear Power Station, forcing several reactors offline in a rare, non-nuclear shutdown.

Four of the plant’s reactors shut down after swarms of jellyfish clogged its pumping stations. It isn’t the first time the creatures have thwarted nuclear plants.

Since its inception, nuclear energy has faced a host of opposition, from oil conglomerates to well-intentioned anti-nuclear-weapons activists to environmental groups. As it turns out, even ocean critters are getting in on the movement.