SAN DIEGO — In the ocean off Coronado, a Navy team has discovered a relic worthy of display in a military museum: a torpedo of the kind deployed in the late 19th century, considered a technological marvel in its day.

But don't look for the primary discoverers to get a promotion or an invitation to meet the admirals at the Pentagon — although they might get an extra fish for dinner or maybe a pat on the snout.

The so-called Howell torpedo was discovered by bottlenose dolphins being trained by the Navy to find undersea objects, including mines, that not even billion-dollar technology can detect....