Here's what happens when US Navy special operators go up against dolphins trained to keep them out of sensitive bases

• The US Navy has been training dolphins and sea lions to detect undersea threats since the 1960s.
• Over the years, the Navy has put those animals up against its most skilled human operators.
• "Those mammals were very real and very scary," a former US Navy SEAL officer told Insider.

At the height of the Cold War, the US Navy turned to an unlikely source to protect its prized warships: dolphins and sea lions.