Under the preferred plan, dolphins would be used only at night and would be accompanied by handlers in small power boats. The dolphins would be trained to return to the boat and alert the handler if they noticed an intruder. The handler would then place a strobe light on a dolphin's nose, and the creature would return and bump the intruder, causing the light to come free and float to the surface as a location marker.
Guards would then be sent to find and subdue the intruder.
Murray said the sea lion-only option was added in response to public suggestions after the use of dolphins was proposed in 2007.
Sea lions would be trained to carry in their mouths a special cuff attached to a long rope and clamp the cuff around the leg of a suspicious swimmer, who then could be reeled in for questioning.
