I love dolphins! There are 40 species of them. 
Me too! How do they communicate?
I am not too sure about that, but, they have well-developed hearing which is adapted for both air & water. 
How fast can they travel in the water?
Not 100% sure, but although they are not quite as flexible as seals, some can travel just as fast as seals. 
What do they eat?
, in that the males are larger than females. They have streamlined bodies and two limbs that are modified into flippers. Though not quite as flexible as seals, some dolphins can travel at . Dolphins use their conical shaped teeth to capture fast moving prey. They have well-developed hearing which is adapted for both air and water and is so well developed that some can survive even if they are blind. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under
their conical-shaped teeth and long beaks to capture fast-moving prey in murky water. They have well-developed hearing that is adapted for both air and water; they do not really rely on vision since the water they swim in is usually very muddy. These species are well-adapted to living in warm, shallow waters, and, unlike other cetaceans, have little to no blubber.
River dolphins are not very widely distributed; they are all restricted to certain rivers or deltas. This makes them extremely