The carapce is pale orange with dense dark red brown spots. Individuals from shallow waters, 0.1–0.5 metres (3.9 in–1 ft 8 in) deep, have a carapace width of only 10–15 millimetres (0.4–0.6 in), while those from 5–15 m (16–49 ft) are 100–140 mm (3.9–5.5 in) wide. Most noteably the 5th pair of legs have been flattened into swimming paddles. Claws are very sharp!

Sandy areas in the surf zone and out on the shelf.

Predator, uses it's very sharp claws to feed upon shellfish, worms and other crustaceans, will also scavenge.

"Biology and Ecology of Ovalipes catharus" (PDF). Bay of Plenty Polytechnic. R. G. Wear & M. Haddon (1987). "Natural diet of the crab Ovalipes catharus (Crustacea, Portunidae) around central and northern New Zealand" (PDF). Marine Ecology Progress Series 35: 39–49.