Dolphin (Red Alert 2)

Bottlenose Dolphins (Tursiops truncatus) are incredibly intelligent marine mammals. Allied scientists realized that the intelligent dolphins would be useful as a swift underwater scout unit when properly trained, and so dolphins became part of the Allied arsenal in the fight against against global communism.

Usage
"Commander, I thought I've seen everything, but this takes the cake. You guessed it - mind-controlled squids. Intelligence informed me that effective countermeasures involves specially-trained dolphins which are now at your disposal. What's next, killer whales?"

- Eva

Being no larger than any other sea animal (less than 15 feet long and weighing less than 1500 lbs), dolphins are basically invisible to radar and sonar, until they get close enough to an enemy unit for them to discern the idiosyncrasies of the dolphin. Due to their natural ability for echolocation, the Allies managed to fit the dolphins with equipment that would amplify the sonar pulses enough to damage Soviet craft.

These attacks were particularly effective against the Soviet giant Squid, due to the squids natural sensitivity to water-based vibrations. The focused sonic attacks of the dolphins caused the squids considerable pain. The squid, disorientated, would release its grasp on any ship it might be holding captive at the time.

Dolphins were also highly effective in groups, as their sonic pulses could damage multiple targets at once. Surrounding a submarine or other naval force with dolphins tended to have a greater than 1:1 damage ratio.

The dolphins were first deployed in when a giant squid attacked a civilian cruise ship. They rescued the ship from being torn apart and went on to harass the Soviet fleet.

Counters
The Soviets soon found that their Sea Scorpions' flak cannons are highly lethal to the dolphins. Torpedoes from Typhoon submarines also works, but rather less efficient when it comes to large schools of dolphins.