It was unexpected to say the least. When two different dolphins being trained for mine detection alerted to a device in a place where their Navy trainers didn't expect, the sent down divers to see what the fuss was all about. What they found was an extremely rare type of torpedo designed during the late 19th century.
The two dolphins, Ten and Spetz, are trained at the Point Loma facility in San Diego, CA, where they, along with other bottlenose dolphins are trained to find underwater mines and explosives primarily by shape. If a suspicious object is found, the dolphins tap the front of the boat with their snout - if no object is found, the dolphins tap the rear of the boat. The dolphins can also take a marker to the mine, so it can either be avoided by ships or inspected by underwater divers.
The torpedo found by Ten and Spetz is known as a Howell Torpedo - named after its inventor Lt. Cmdr. John C. Howell, USN. This torpedo used a heavy flywheel (130 lb.) spun at high speed (10,000 RPM) instead of an engine. This made it cheaper and easier to build, and it produced no wake, unlike competing designs. It did, however require large winches to spin up the flywheel, it was quite noisy, and it didn't have the performance of other designs. The Navy ordered 50 Howell torpedoes - these were the only examples made - for testing, before competing designs copied and refined Howells problems.
Before this discovery, there was only one surviving example of a Howell torpedo - on display at the Undersea Museum in Keyport, WA.