The two basking sharks, which typically reach lengths of around 25 feet, were spotted by those at the beach in Keem Bay on County Mayo's Achill Island in Ireland
Video footage which was posted to Tik Tok shows the fins emerging from the water, with one following the other closely, as a group of people look on in astonishment.
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A child can be heard saying “Oh my god!” as the sharks swim by slowly.
Are basking sharks dangerous?
Although the sight of shark fins is alarming, basking sharks are completely harmless.
They are one of three types of shark to feed on plankton, opening their enormous mouths and filtering plankton through their gill rakers.
Their name derives from the fact that they stay close to the warmer waters of the surface to feed, and appear to be ‘basking’.
They are common worldwide in boreal to warm-temperate waters, and sightings are common off the coast of Cornwall, the Hebrides and the Isle of Man.
While basking sharks are harmless, they are huge animals and their skin is extremely rough, so caution is urged during any encounters.
The basking shark is listed as a vulnerable species by the IUCN (International Union for Conservation of Nature) list.