Sentence:  Upon getting into a "<WSD>gam</WSD>" of whales, this boat, together with that of one of the mates, pulled for a single whale that was seen at a distance from the others, and succeeded in getting square up to their victim unperceived. 
Meaning of the word marked with <WSD> tags:  (Collective noun used to refer to) a group of whales, or rarely also of porpoises; a pod.