An 11m-long sperm whale's unexpected encounter with an exploration team in the Gulf of Mexico has become a YouTube hit with nearly 1.5million views so far.

The crew of the Exploration Vessel (E/V) Nautilus were on a routine trip measuring natural methane and hydrocarbon plumes in the Gulf of Mexico on 14 April when the giant approached them.

Footage shows the mammal swimming around the crew's remotely operated vehicle (ROV), Hercules, coming up close to the equipment and circling the machinery several times, while the crew and pilot excitedly discuss the encounter.

Despite the whale's size, it managed not to come into contact with any of the equipment.

When asked why the creature had come so close, the scientists' best guess was that because sperm whales have such excellent hearing, it could have been attracted to the tiny sounds made by their equipment.

The E/V Nautilus and its crew are part of a much larger expedition organised by Dr Robert Ballard, a National Geographic Society Explorer-in-Residence and President of the Ocean Trust, to explore and chart different ocean sites from the Gulf of Mexico to British Columbia.

The public, scientists and students will be able to watch the expeditions via the Nautilus live website.