Seals, octopuses, jellyfish and more

Day octopus

Octopus cyanea

A reef octopus that hunts by day on Indo-Pacific coral. Watch its colour change near its den, give it space, and never touch or feed it.

Least ConcernIn 35 Atlas countries

Least Concern (IUCN, 2018) means it is not at high risk of extinction worldwide today.

Day octopus beside a coral head on a sandy Red Sea reef — Photo: Tom Heijnen, iNaturalist, CC BY

Red day octopus beside a rock and a pencil urchin in Hawaiʻi — Photo: Robin White, iNaturalist, CC BY

Day octopus stretching its arms across sand between corals — Photo: Julien Renoult, iNaturalist, CC BY

Day octopus resting among corals in French Polynesia — Photo: Henrik Kibak, iNaturalist, CC BY

Day octopus standing tall on a shallow reef in the Andaman Islands — Photo: Rohan Arthur, iNaturalist, CC BY

Photos show the species, not always the places on this page.

Length

Body (mantle) up to about 22 cm (8.7 in); with arms, large animals may reach about 1 m (3 ft) across. Most are smaller

Weight

Typical weight not reliably measured, and most seen on reefs are much smaller; largest recorded about 6 kg (13 lb)

Next to a person

The body alone is up to about the length of an adult's forearm; most are smaller

What it eats

Mainly crabs, plus clams, snails, mantis shrimps, shrimps and sometimes small fish.

Around people

Calm, give space

How it lives

The day octopus lives alone in a den in coral or rock and hunts mostly by day, with peaks at dawn and dusk. It pounces on crabs, or spreads the web between its arms over a coral head and feels inside with its arm tips. Goatfish and groupers sometimes hunt with it. Like other octopuses, adults usually die soon after breeding, and the female guards her eggs.

Where it goes

The day octopus does not migrate. Adults are sedentary and keep to dens in a small patch of reef. Across the south-west Indian Ocean, from Kenya to Madagascar and the Seychelles, the genes are well mixed, probably because the tiny young drift in the plankton before they settle.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

The day octopus lives on tropical reefs from eastern Africa and the Red Sea to Hawaiʻi, mostly in shallow water but recorded down to about 150 m. Samples from 20 sites in Kenya, Tanzania, Mozambique, Madagascar, Mauritius, Rodrigues and the Seychelles form one connected population. It is Least Concern, but it is still fished on many reefs. In Hawaiʻi it is called heʻe.

Meet it respectfully

Watch calmly from a little distance and let the octopus stay in or near its den. Never touch, poke, pick up or pull an octopus from its hole, and do not move the shell pile outside its den. Never feed or chase it, even for a photo. If it flashes colour, jets away or inks, you are too close.

Fun fact

Tap the bulb to light it up.

Sources for this page

Facts checked 26 September 2026. Photos: Unsplash licence, or Creative Commons as shown on each photo.

For partners

Work in ocean travel?

We are always happy to hear from exceptional local operators, accommodation, conservation organisations and destination experts. If your work fits responsible, small-group ocean travel, we would love to learn more.

Partner with Ocean Calling

Not sure where to go? Get your Ocean Match

from CHF 19

Find my match →