A group of dolphins is called a pod.
A pod usually is formed of around 12 dolphins, and it is the usual social group of dolphins.
However, when a group of pods joins in places with an abundance of food, they can reach up to one thousand individuals forming a large group which is called a superpod.
Superpods are not for a long time, and they dissolve after a while.
Additionally, another way to call a group of dolphins is “school.”