The operators of a deep-sea research submersible got a big surprise when a huge whale unexpectedly appeared close to their vehicle patrolling the deep-sea.

The encounter took place on the 15th April 2015, when the whale approached a remotely-operated vehicle called Hercules that was diving below the Gulf of Mexico off the coast of Louisiana, US.

The sperm whale appeared at a depth of 598 metres, still relatively shallow for the species, which can dive as deep as 2000-3000m on the hunt for prey such as squid.

Sperm whales are the largest of all toothed whales, and males are larger than females.

Encounters between sperm whales and ROVs are incredibly rare, say scientists onboard the E/V Nautilus, which was monitoring the incident.

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