There are two species of octopi that are very symilar: the Wunderpus Octopus and the Mimic Octopus.

Wunderpus Octopus: they can be found in the Coral Triangle-an area, including Indonesia, Malaysia, Papua New Guinea, the Philippines, Timor-Leste, and the Solomon Islands. The Wunderpus Octopus arms are 5x longer than mantle length. They both like to bury themselves in the sand, and go deep underwater (20m). The Wunderpus use their camouflage to creep up on unsuspecting prey.

Mimic Octopus: they are found throughout the Indo-West-Pacific Ocean, from the Red Sea to Samoa. Their arms are 7-10x longer than the mantle length.

The most important difference is the pattern, color and shape of the eyes. The Mimic Octopus has a bright and continuous line along the base of the suckers. The teardrop ring in the middle-ish area of the mantle and the white “U” is on the end.
The Wunderpus' eyes are shaped like a Y while the Mimic's eyes are shaped like a U.