It should be noted that the theory of dolphins getting "high" off puffer fish is highly controversial as others have mentioned that tetrodotoxin, the neurotoxin released from puffer fish, is famous for causing paralysis making it more of a poison as opposed to a good time. It is reportedly more potent than cyanide. In fact, a study published in 1990 reported tetrodotoxin as the cause of death of two Atlantic dolphins found dead in a lagoon (Hokama et al., J Clin Lab Anim. 1990).
So what exactly are those dolphins doing with the puffer fish in the BBC documentary??
Hokama et al., Causitive toxin(s) in the death of two Atlantic dolphins. J Clin Lab Anal. 1990;4(6):474-8.
The paralysis - due to blocking conductance of action potentials in peripheral nerves - could be similar to a dentist office visit where they give injections to block pain. Maybe it feels nice to them?
I'd also be interested to see if it's only this pod that displays the behavior or if this is ubiquitous.
Don't quite follow your logic here. Evidence that two dolphins may have died from ODing on puffertoxin is proof that they could not have been trying to get high?