Emancipation — Craig Marley

It was the preeminent achievement in interspecies communication. Rather than trying to decipher their language, as so many had failed before. ... teach them ours.
Book 1. of the Talking Dolphin series.
2020: Tijuana, Mexico/San Diego: Under Executive Order from President Trump, the US Customs and Drug Enforcement Agencies added thousands of personnel to stop the flow of illegal drugs. In response, the cartel deployed enslaved dolphins to smuggle their heroin across the border. Using his breakthrough dolphin communication techniques, Greg Mason, his team of talking dolphins and former SEALs must rescue the enslaved dolphins and destroy the cartel base of operations.