December 2014 (ROTM#72) Durban, South Africa

Do you ever wonder why there's always 'no swimming' and 'keep away' signs next to structures such as piers, groynes and jetties on beaches? Most people think it's because they can get hurt falling on them, or bumping into them, which is true, but these structures are also magnets for rip current formation. Often longshore currents get deflected offshore when they flow into these structures, or wave refraction and shadowing processes cause circulating rips to form next to them.

This Google Earth picture shows rip currents on either side of some piers on the beach in Durban, South Africa. The piers stick about 150 m into the water. Those rips are huge and no doubt flowing pretty quickly! Best to keep away from structures when you're swimming, even in lakes when there's breaking waves.

Massive rips heading out along the piers