"Some species of dolphin can swim at up to 56 kph/35 mph, helped by special streamlining modifications of the skin."
http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0007583.html
"Common Dolphin Length:
Weight:
Speed:
Life Span:
7-8 ft.
180 lbs. (Bay of Gibraltar 100-140 only as mostly immature)
40+ mph.
25 years."