WW2 has just started. U-Boats prowl the Atlantic for merchant shipping.
One such boat, U-27, is bombed and strafed by a SuperMarine Stanraer Bi-Plane Bomber on Oct. 4 1939. The uboat suffers only minor damage, but the bomber radios in to a trio of old destroyers about 18 miles away. About 25 minutes later, U-27, after having crash dived, surfaces to periscope depth to look for the meandering bomber they thought would be there. Instead, THIS is what they see:
A trio of old I and E class destroyers rapidly approaching at only 2000 yards away.
U-27 fires three torpedoes at the leading destroyer, which is just 1,500 yards from her now. Steam powered Mk 1 torpedoes enter the frigid English Channel water. The torpedoes hit home.

The target is obliterated. The British, now aware of a Uboat in the vicinity, pick speed and search.
The 2nd destroyer, now leading the force, fired at a periscope. I-27 quickly fires her last readily available torpedo, which does its job and still explodes.
The remaining destroyer, on which the crews were a mix of frightened and furious, try and try to pick up a decent ASDIC of the submarine. But before this, U-27 slips away to the West.