Prominent among the family Ursidae is a polar bear that is adapted to a highly specialized semi-aquatic lifestyle. Although it is a bear yet it is listed as a marine mammal precisely due to the fact that it spends 50% of its life on ice floes and is able to swim as far as 90 km (60 miles).
urchin. 1  a mischievous boy. 2  any small boy or youngster. 3  sea urchin. 4  either of two small rollers covered with card clothing used in conjunction with the cylinder in carding. 5  Chiefly British Dialect. a hedgehog. 6  Obsolete. an elf or mischievous sprite.
Starfish are echinoderms (spiny skinned sea urchins). They are also known as sea stars and are not really fish despite the name been given to them. Starfish cannot swim, and they do not use gills to breathe. For more information on these interesting sea urchins, see the fact sheet below. All echinoderms have five-point radial symmetry, which means that their body plan has five sections arranged around a central disk. 2  Starfish are found in the deep blue sea of the ocean and shallow water as well.