Sentence:  Given that a large number of all rescues conducted by Surf Life Saving Australia (SLSA) occur in <WSD>rips</WSD> (a <WSD>rip</WSD> being a relatively narrow, seaward moving stream of water), this is critical surf-safety information (Surf Life Saving Australia, 2005). 
Meaning of the word marked with <WSD> tags:  A strong outflow of surface water, away from the shore, that returns water from incoming waves.