An octopus has made a daring escape from New Zealand's National Aquarium in Napier.

Inky, a male common New Zealand octopus, slipped through a gap in the top of his enclosure before travelling across a wet floor, down a drain and into the sea.

The aquarium has a system of reticulated drains that circulate seawater from the ocean.

Aquarium Manager Rob Yarrell told Newshub the getaway occurred during a routine tank check by staff.

"Octopus are really intelligent animals, very inquisitive, and they also tend to explore whenever they get the chance," said Mr Yarrell.

"Giving him just a little gap was enough for him to get out and we noticed the wet trail across to one of our drains."

Inky is about the size of a rugby ball, but Mr Yarrell said octopi can stretch themselves to extremes.

"It's only restricted by the size of its beak, that's the only part they can't make smaller."

Mr Yarrell said it's now safe to assume Inky is merrily roaming the sea floor.

Newshub.