I concur entirely, the cure would be worse than the disease The way destroyers work in the game is actually an almost perfect recreation of the capabilities of world war 1 and 2 destroyers on the operational-strategic scale that the game works on. Destroyers CANNOT hunt subs in the real world using WW2 technology. SONAR (nee ASDIC) has a useful detection range of 5-10nm in that era. The North Atlantic is some 10,000,000 sq miles in area. Allowing each DD to cover 100 sq miles would require 100,000 destroyers to search the ocean. I think with 100,000 civ3 DDs I could find any sub (in the game) by the simple - and effective in the game - mechanism of just sailing around until I bumped into them. That - blundering into subs - is how you search in civ3 for a sub, until you get current technology ships - AEGIS. IMO the anti-sub capability given to the AEGIS units is too great - a 2 tile radius is HUGE - but it's not too bad. Alternatively, do what worked throughout WW2. Escort your valuable ships. If the subs try to attack, you will probably kill them. If the subs just sail around, no great harm is done. If they try to block a port, then go and patrol the choke point and open up the tiles again.