The Argentinian submarine successfully landed her reinforcements at Grytviken, under moonless cloud cover in the pre-dawn hours of 25 April, and was underway by 0500. "Antrim"′s aircrew, which included Lieutenant Chris Parry, anticipated that "Santa Fe" would unload her troops under the cover of darkness and would withdraw at first light through Cumberland Bay without submerging, due to the threat of icebergs. They suggested re-fitting their Wessex with radar, which had been removed to transport the SAS, and intercept "Santa Fe" as she left the bay. Captain Young thus brought his three warships some 25 miles north-east of Cumberland bay and prepared his helicopter force for anti-submarine action. He now had at his disposal, besides "Antrim" Wessex, three Wasps (one aboard "Plymouth" and two on "Endurance") and two Lynxes (aboard "Brilliant"). At 0855, the submarine was located by "Antrim"'s Wessex using radar and engaged with depth charges. One charge bounced off the boat's deck but the other exploded alongside, rupturing the port ballast tank and piercing an external fuel tank. Now unable to dive, Bicain was forced to reverse course towards Grytviken.