There are a lot of world records out there for swimming. There are more than 20 different swimming events. You have to be more specific for what time you want.
Hampshire
The sailfish is the fastest swimming ´thing´on earth. It can reach speeds of 120 kph.
I have found that the fast skins are the fastest.
squids.....
dolphin
The dolphin
The three fastest in order are California, Illinois, and Texas.
The Common dolphin is generally the fastest swimmer of the dolphin family.
Where have you been? Michael Phelps.
They are the fastest swimming sharks
It is the fastest.
Crocodiles are the fastest fresh water animal in terms of hunting its prey. Despite of their huge size, Crocodiles are capable of swimming 3 times faster compared to an Olympic swimmer.