The Sea Shepherd was the first ship of the Sea Shepherd Conservation Society, acquired in 1978. It was a former fishing trawler. Its most notable act was the ramming of the pirate whaling vessel the Sierra. The incident went to a Portuguese judge, who ordered that the Sea Shepherd be turned over to the owners of the Sierra to repay the damages. Unwilling to let his vessel fall into the hands of whalers, Captain Paul Watson scuttled the vessel.
The ship was purchased with a grant from Fund for Animals. In 1979, the Sea Shepherd departed Boston in pursuit of the notorious whaling ship Sierra. Captain Watson planned a controlled ramming of the whaler, but the Sierra fled to Portugal with the Sea Shepherd tailing it all the way. On July 16, 1979, the Sea Shepherd ambushed the Sierra as it was coming out of port and Captain Watson warned the whalers of his intent to ram. He then proceeded to ram the bow of his ship into the Sierra three times, severely damaging the whaling ship. The listing Sierra called for assistance from the Portugal navy. The Sea Shepherd attempted to flee to Spanish waters, but the navy forced them to return to Portugal. A judge ordered that the Sea Shepherd be turned over to the owners of the Sierra. Captain Watson refused to see his ship be turned into a whaler and scuttled it on December 31, 1979. The Sierra was repaired, but sunk by a limpet mine in February, 1980.