Russia's defence ministry is looking for specific new recruits, and the standards have been set high.
The Russian government revealed on Wednesday that it seeks five dolphins in perfect condition as its newest military members as the country strives to revive its Soviet-era use of sea mammals for military tasks.
The military has opened the bidding on a 1.75 million ruble ($24,000) contract to deliver dolphins to the military in the Crimean port city of Sevastopol by August 1, according to a document uploaded Wednesday to the government's procurement website.
According to public contract documentation, it is seeking two female and three male dolphins between three and five years old with perfect teeth and no physical impairments.
An unnamed source told RIA Novosti state news agency in March 2014 that new training programmes were being designed to make the dolphins serve Russia's military interests.
Dolphins were used by the Soviet Union and United States at the height of the Cold War, having been trained to detect submarines, underwater mines and spot suspicious objects or individuals near harbours and ships.
Retired colonel Viktor Baranets, who observed military dolphin training in the Soviet and post-Soviet eras, said that the sea mammals were part of the broader Cold War arms race between the USSR and the United States.
"Americans looked into this first," Baranets told AFP. "But when Soviet intelligence found out the tasks the U.S. dolphins were completing in the 1960s, the defence ministry at the time decided to address this issue."
Baranets added that combat dolphins in the Soviet era were trained to plant explosive devices on enemy vessels and knew how to detect abandoned torpedoes and sunken ships in the Black Sea.
Crimea, which Russia annexed from Ukraine in March 2014 amid international indignation, has housed this training facility since 1965.
The training centre was severely neglected after the collapse of the Soviet Union, Baranets said, and its dolphins were reportedly sold to Iran.
The Ukrainian navy reestablished the centre in 2012 but Russia's landgrab two years later saw Crimea's combat dolphins fall under Moscow's control.
The defence ministry could not be reached for comment on Wednesday.
The U.S. navy also uses sea mammals to carry out military tasks, with sea lions deployed to Bahrain in 2003 to support Operation Enduring Freedom after the 9/11 attacks.