Dolphins are considered to be one of the most intelligent animal species around, and it seems they are using their sharp intellect to get 'high'. You read that right.
In scenes filmed for a documentary titled "Dolphins: Spy in the Pod", dolphins can be seen carefully manipulating a certain kind of puffer fish which, if provoked, releases a nerve toxin. If taken in small amounts, this toxin can produce a narcotic effect. These smart dolphins seemed to have worked out the right amount to enter a trance-like state. They can be seem chewing on the puffer fish and passing it between one another.
Rob Pilley, a zoologist who also worked as a producer on the series, explained
This was a case of young dolphins purposely experimenting with something we know to be intoxicating. After chewing the puffer gently and passing it round, they began acting most peculiarly, hanging around with their noses at the surface as if fascinated by their own reflection.
With intellect and skills only second to humans, it makes sense how dolphins figured the key to their cheap thrills.