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Dolphins have a pair of pectoral fins behind the head, which they use for steering.  Primary propultion comes from the tail, which bears horizontal flukes made from subcutaneous dermal tissue; movement through the water consists of vertical sweeps of the tail.  Speeds of dolphins have been estimated at  23-25 mph (37-40 km/h), which is enough to allow for “porpoising” i.e. the leaping of the animal out of the water at various times.  Some species have been observed to reach higher speeds.

Dolphins have a pair of pectoral fins behind the head, which they use for steering.  Primary propultion comes from the tail, which bears horizontal flukes made from subcutaneous dermal tissue; movement through the water consists of vertical sweeps of the tail.  Speeds of dolphins have been estimated at  23-25 mph (37-40 km/h), which is enough to allow for “porpoising” i.e. the leaping of the animal out of the water at various times.  Some species have been observed to reach higher speeds.

Most species of dolphins also bear a dorsal fin on their backs, made from the same dermal tissue as the tail flukes, and is believed to act as a stabilizer while moving.  In some species (orca, grampus), the dorsal fin is rather large relative to the size of the body; in several others the fin is a small ridge extending over a portion of the back (river dolphins), or entirely non-existant (right whale dolphin). Bottlenose dolphin males have been observed working in pairs or larger groups to follow and/or restrict the movement of a female for weeks at a time, waiting for her to become sexually receptive. Their sexual advances can become so aggressive that they gang rape unreceptive females, sometimes drowning them in the process. Most of the time, however, the pairs/groups engage in ardent sexual play with each other.

Most species of dolphins also bear a dorsal fin on their backs, made from the same dermal tissue as the tail flukes, and is believed to act as a stabilizer while moving.  In some species (orca, grampus), the dorsal fin is rather large relative to the size of the body; in several others the fin is a small ridge extending over a portion of the back (river dolphins), or entirely non-existant (right whale dolphin).

Dolphins range in size from Maui's dolphin (''Cephalorhynchus hectori maui'') of [[New Zealand]], which at 3.9 feet in length makes it the smallest cetacean of any kind; to the male [[orca]] or killer whale (''Orcinus orca''), which can reach lengths in excess of 30 feet and weigh in at 6 tons.

Dolphins range in size from Maui's dolphin (''Cephalorhynchus hectori maui'') of [[New Zealand]], which at 3.9 feet in length makes it the smallest cetacean of any kind; to the male [[orca]] or killer whale (''Orcinus orca''), which can reach lengths in excess of 30 feet and weigh in at 6 tons.