Lucien B. McDonald, Lamprey cleared Fremantle 21 May and entered the Java Sea bound for her patrol area in the Siam Gulf.

On 28 May Lamprey and USS Blueback closed for a coordinated gun attack which damaged and set afire a 600-ton escort ship.

The submarine returned to sea 26 July for her third war patrol and spent most of her time searching for targets along the Gulf of Siam.

She entered the Singapore area 8 August to patrol west of Pengiboe Island where she sank a small craft with gunfire.

[6] Some years ago, Argentinian officials disclosed that a group of tactical divers had carried out an incursion on the Falkland Islands on board the Santiago del Estero in October 1966.