Sentence:  On the afternoon of the date mentioned the wind was blowing offshore and the tide was running in, forming <WSD>sea pusses</WSD> at intervals along the shore. We swam out to where the bar had been. Finding that it had shifted, we turned to come back and found that the ide had carried us into a <WSD>sea puss</WSD>, and that we were being swept seaward. 
Meaning of the word marked with <WSD> tags:  A strong seaward current; a riptide or undertow, especially as results when a sandbar formed by waves suddenly gives way(,) and which is dangerous to swimmers.