In the Fleet’s Operational Marine Mammal Systems (MMS), the Navy uses dolphins and sea lions to find and mark the location of underwater objects.

Dolphins are essential because their exceptional biological sonar is unmatched by hardware sonars in detecting objects in the water column and on the seafloor. Sea lions are used because they have very sensitive underwater directional hearing and exceptional vision in low light conditions.

Both of these marine mammal species are trainable for tasks and are capable of repetitive deep diving.

Some of the objects the animals find are expensive to replace. Others could present a danger to Navy personnel and vessels. The dolphins and sea lions work under the care and close supervision of their handlers and are generally trained for a particular operational capability called a “system.”

(The term “system” is engineering jargon for a collection of personnel, equipment, operations processes, logistics procedures, and documentation that come together to perform a specific job.)

However, animals may be crossed-trained for more than one system to better serve the needs of the Fleet. The term “mark” (MK for short) is military jargon for a type of thing within a category. There are 5 marine mammal systems called MK 4, MK 5, MK 6, MK 7, and MK 8. MK 4, MK 7, and MK 8 use dolphins; MK 5 uses sea lions; and MK 6 uses both sea lions and dolphins.

These human/animal teams can be deployed within 72 hours of notice and can be rapidly transported by ship, aircraft, helicopter, and land vehicles to potential regional conflicts or staging areas all over the world. They regularly participate in major Fleet exercises.

These animals are released almost daily untethered into the open ocean, and since the program began, only a few animals have not returned.”

The Mark 6 System

• MK 6 MMS was first operationally deployed with dolphins during the Vietnam War from 1971 to 1972, and Bahrain from 1986 to 1987.

• MK 6 has now expanded to include specially-trained sea lions to locate water-borne intruders and suspicious objects near piers and ships that pose a possible threat to military forces in the area. They have been shown to be effective under and around ships, piers, and in open water.

• The sea lions were deployed to Bahrain as part of the effort to support missions under Operation Enduring Freedom.