September 2021 (ROTM#153) Manly Beach, Sydney, NSW, Australia

In ‘the old’ days, the only aerial images we had of beaches were those taken from planes and helicopters and, more formally, from commissioned series of aerial photographs. However, drones have changed all that. All of a sudden we’re getting more imagery from more places showing us amazing things – like the fact that there are sharks in the ocean (who would have thought!). But every now and then, drones capture incredible footage of rip current circulation like this one, sent to me by Tony Gibbs (@tonedrone on Instagram).

There’s been similar drone pictures taken of rips showing what seems to be this horrific vortex of doom that will pull you out from the beach, spin you round, and then drag you down to the bottom. Well they don’t do that. If you click on the photo you can watch a movie taken by Tony that shows that the flow is slow, but steady. We also know that you won’t get pulled under…surfers can paddle across these rips quite easily.

From a scientific point of view, the physics behind these patterns is both fascinating and complex. These types of rips tend to occur on days when the surf is big and coming from an angle to the beach. This creates a strong longshore current that sometimes becomes unstable and sends these rip pulses offshore. The spinning action is called vorticity. These rips don’t last for long, but you can see they are strong enough to carry plumes of sediments and presumably, swimmers, offshore. The good news from a safety perspective is that you probably wouldn’t be swimming on days like this – the lifeguards would close the beach to swimming.

It’s not as bad as it looks.