One of the original set of Avalon Hill "Adult Games" which include Gettysburg, Tactics II, Verdict & Dispatcher.
The basic game pits one U-Boat against one Destroyer. They maneuver around each other with limited knowledge of the other's depth and position in an attempt to gain a critical hit.
The Multi-ship game pits 3 U-Boats against 3 Destroyers.
There was a revision to the rules in 1961 version of the game. The first set of rules (1959) was in a Booklet format and the revised rules (1961) were in a Large single sheet folded. Difference in the rules ranged from where torpedoes could be placed and the damage from Near Missed depth charge attacks.
Board: 19 x 14 square grid
Pieces: 3 U-Boats, 3 Destroyers