So what is a rip? It is a current flowing away from the beach in the direction of the open sea and is the method by which water coming into the beach in the surf zone (i.e. the broken water) returns to the sea. Much more is known about rips than in earlier times due largely to the research by Dr Rob Brander from UNSW (see http://www.scienceofthesurf.com/drrip.html).
Briefly, rips are often unpredictable; their characteristics depend in part on the nature of the sea bed (rocky, sandy, the presence of gullies), atmospheric pressure and the state of wind and tide. Some beaches have permanent rips but, mostly, they are changeable which is why lifesavers put the flags in the safest part of the beach and why they may change their position as rips develop. Rips can vary in intensity and can develop without warning – these are called ‘flash rips’.
Rips can often be identified by discoloured water moving away from the beach (caused by sand, dirt, flotsam, etc) and no – or less intense – breaking waves. It may appear to be the best place to swim as the waves are not so big – but this is a big mistake as rips can carry you away from the beach and into deep water. Check out this pic – most rips are not this obvious.
Also check out this video clip: https://www.youtube.com/watch?v=IeJLRdJpS1M. Despite his Canadian accent, Rob is a dinky-di Aussie surf lifesaver as well as being an academic surf expert.
So what do you do if you are caught in a rip? While a precise answer depends on how strong the rip is and how strong a swimmer you are, as a general rule, don’t panic, just go with it, float on your back and put up your hand so the lifesavers can see you and you’ll be fine. Chances are that the lifesavers will have noticed the rip (and you in it) and will be alongside you in no time at all. How far the rip extends seawards depends on how steep the beach gradient is but, even in a low gradient beach where the breaking waves extend a long way out, the rip will dissipate at no more than about 200 metres (don’t worry, you won’t end up in New Zealand). You can then swim parallel to the beach for a short distance and come back into the beach through the broken waves. Some rips even turn around and send water (and you) back into the beach – but not all of them.
To summarise, don’t panic and don’t fight a rip. Few of us are strong enough swimmers to swim against or even across a rip. And always remember to swim between the flags. While there were 54 drownings at Australian beaches in 2013, there were none at all in between the flags. And, in most cases, the victim was caught in a rip.
There have been, on average, 20 deaths per year over the period 1890 to 2013 as a result of rips (and only one from shark attack).