Dolphins eat a variety of foods, depending on the species and the availability of prey, but they most frequently dine on squid, fish and crustaceans.  Dolphins that live along the coasts mainly consume fish and invertebrates that live on the bottom of the ocean, while those that live offshore enjoy fish and squid. 
"Amazon dolphin eating fish" by frank wouters - Flickr. Licensed under CC BY 2.0 via Commons - https://commons.wikimedia.org/wiki/File:Amazon_dolphin_eating_fish.jpg#/media/File:Amazon_dolphin_eating_fish.jpg
Dolphins sometimes work in teams to capture prey, encircling schools of fish or herding them toward the shore or a sandbar to make it easier to catch them. A dolphin may stun its prey by using its tail to flip a fish out of the water. Dolphins don't chew their food. They either swallow prey whole or drag their prey along the bottom of the ocean to break off pieces before consuming them. Sometimes dolphins follow fishing vessels where they feed on discarded fish.  They also use echolocation to find prey.