Scientists say they have discovered what might be a new species of octopus while searching the Pacific Ocean floor near the Hawaiian Islands.

A team found a small light-coloured octopus on February 27 at a depth of about 4km in the ocean near Necker Island, Michael Vecchione, of the National Oceanic and Atmospheric Administration, said on Saturday.

The octopus did not have fins and all of its suckers were in one row on each arm, Vecchione said.

The octopus "did not seem very muscular" and was light colored, he said.

"This resulted in a ghostlike appearance, leading to a comment on social media that it should be called Casper, like the friendly cartoon ghost. It is almost certainly an undescribed species ... , " he said in the statement posted on Wednesday.

It is unusual to find an octopus without fins so deep in the ocean, said Vecchione, who noted that the previous depths at which an octopus without fins was found were all less than 4km.

Two scientists he has consulted "agreed that this is something unusual and is a depth record ... ," said Vecchione, who is with NOAA's National Systematics Laboratory.

The octopus was discovered during a search of the ocean floor by a remotely operated vehicle from NOAA's Okeanos Explorer, he said.