Breathtakingly gigantic jellyfish spotted off English coast

A marine biologist got the surprise of her life when she swam off the southwestern coast of England and came across a jellyfish the size of a human.

Lizzie Daly, who was surveying an estuary as part of a campaign to document her "encounters with some of the U.K.'s most charismatic marine species," saw the barrel jellyfish near Falmouth.

"We just swam with a giant barrel jellyfish!" she exclaims in a two-minute video. "I've never seen a barrel jellyfish or any jellyfish that big! It was the size of my body, and it was the best thing I've ever done!"

Considered one of the largest jellyfish species, barrel jellyfish can often be found swimming off the coast of the U.K. during the spring, according to the Wildlife Trusts. The translucent marine animals usually grow to the size of trashcan lids, which makes the one that Daly saw particularly rare. The conservation organization adds that though the jellyfish's sting is not harmful to humans, people who do come across one should exercise caution.