RIP IS A FLOW OF WATER OUT TO SEA
Every year 20 00 people are rescued and at least 20 people drown in rip related scenarios around the United Kingdom. The deadly nature of rip currents doesn't come from rips themselves - but lack of knowledge:
Never swim against the current.
A rip current is a narrow channel of water that can flow hundreds of metres out to sea (that's way beyond the surf zone). As water surges up the beach with a breaking wave, it flows along the shoreline until it finds the path of least resistance back to sea. These paths of least resistance can be headlands, cliffs, reefs or gaps in beach sand banks. Once the water finds these paths, it will flow back to sea at speeds of up to 2.5 metres per second. That's over 100 metres in a minute.
For surfers, rips are a fantastic way of getting out back (beyond breaking waves) quickly and effortlessly. For those who are unaware or unsuspected, they can be quickly dragged out to where they don't want to be. Without a basic understanding of rip currents, most people in this situation would immediately start swimming back to shore - but not even gold medallists can keep that up; and so most deaths occur because people have been swimming against the rip, without going anywhere, and tiring to the point of exhaustion.
The most common type of rip current in the United Kingdom is a sandbar rip. They form when waves break on the beach, and water flows along the shore until it reaches a gap between the sandbars where it flows out to sea. As the tide falls, sandbar rips become more powerful - this is because the shallower water over the banks increases waves breaking and forces water through the gaps at faster speeds.
For most people, the sensation of being caught in a sandbar rip current is being pulled straight out to sea. However, recent research suggests that this only happens 1 in 5 times, when someone is in a "rip exit" - where water flows straight out to sea and dissipates beyond the surf zone. The rest of the time, the rip will move in a circular pattern (just like an eddy); so the rip will take you out to sea, then parallel to the shore and then back towards the beach and waves. This has huge ramifications for how you should approach escaping a rip current; but it also adds a new complication. Different tactics suit eddies and exits, and knowing which you are in is often difficult to tell - so the safest approach is often to swim perpendicular to the current (which often means swimming parallel to the shore).
hOW TO SPOT RIPS
The single best way to spot rips is to watch the water from high(er) ground and wait for a set of waves to come in. Bigger waves make more powerful rips, so it is better to identify rips with ground swell waves rather than wind swell waves. Waiting for a set, often means just that - waiting. So here are a few things you can look out for in the meantime.
AT low tide
Look for gaps between sandbars - keep in mind that rips will occur as the tide rises.
In river mouths
The outflowing water will carve a deeper channel into the sand and rips will form.
Anything obstructing stream, such as headlands, groynes and piers, can create rips.
Once you have figured out where rips might form, it is useful to know how to spot if one is present. The most obvious and easily identifiable feature is a gap between waves - this is the sign of rips flowing in deeper water. As the water is flowing out to sea, it might be discoloured with sand or sediment (and sometimes, sadly, rubbish).
The best way of identifying rips is to understand the three individual features of the rip...
The section nearest the beach, it is often shallower than the water around it. Water from the feeder is fed into the neck.
This is typically the narrowest and fastest feature of the rip. It is often darker than the surrounding non-rip water because it is deeper.
As the neck flows beyond the surf zone it dissipates into the head - a characteristic arc of foam/sediment disappearing into the water around it.
If you can identify just one feature of a rip, it will help you put together the rest of the current. Just remember that most beaches have more than one rip, so if you spot one - keep looking!
When waves break at an angle to the beach, it generates a longshore current and this flows along the coast (sometimes for miles) until it is deflected by an obstructing topographical feature like a headland or groyne. Although sandbar rips are the commonest, topographical rips are the most dangerous as more powerful rips are generated by the same sized waves. This means a topographical rip can travel twice as far beyond the surf zone as a sandbar rip would travel (if they were generated by the same wave). The worst angle for this is waves travelling at 45 degrees to the beach, so pay particular attention to swell direction if you surf beaches with features like headlands, groynes or piers.
A note on groynes...
The tide can affect rips too, particularly those generated by groynes. At low tide, no rips will be present if the groyne is out of the water. As the sea levels start to rise and submerge the groyne, rips will grow. The shape and position of groynes also affects rips. If the space between groynes is roughly two times their length, the speed will be 25% less than if the groynes were four times their length apart. To clarify that, the wider the groynes are apart, the bigger the rips can grow - when water hits the groyne, the further along the structure it can flow the longer the rip will form. Groynes that extend far beyond the surf zone will create rips that travel twice the distance - far longer than sandbar rips. So unless you want to get into deep water, stay away from structures heading out to sea.
HOW TO ESCAPE A RIP
NEVER swim against the current.
Escaping a rip is all about having the know-how to not panic. If you panic, you expend valuable energy and you'll probably end up swimming directly against the current. The best advice is to swim across the current towards breaking waves, and use them to get back to shore.