 More U-boats were assigned to the 29th flotilla when improved anti-submarine warfare (ASW) measures along the east coast of North America ended the Second Happy Time.When a Short Sunderland found "U-559", the aircraft summoned five destroyers able to maintain contact and drop 150 depth charges over ten hours, until the submarine attempted to sneak away on the surface at night.Waiting destroyers open fire as soon as the U-boat surfaced and the U-boat crew abandoned ship.