Sentence:  He and Gerald usually challenged the <WSD>rollers</WSD> in a sponson canoe when Gerald was there for the weekend ; or, when Lansing came down, the two took long swims seaward or cruised about in Gerald's dory, clad in their swimming-suits ; and Selwyn's youth became renewed in a manner almost ridiculous,nb.... 
Meaning of the word marked with <WSD> tags:  A large, wide, curling wave that falls back on itself as it breaks on a coast.