On the swimming strategies to escape a rip current: a mathematical approach

Abstract

Rip currents represent significant hazards to swimmers all around the world. The danger arises when a misinformed swimmer uses an inadequate strategy to escape the rip, such as fighting the current directly. This can lead to fatigue, panic, and in some cases drowning. There exists a range of strategies put forward by experts (both lifeguards and scientists) to escape rip currents. However, these recommendations are based on a limited number of scientific studies and there is still much discrepancy surrounding the best strategy to escape a rip. Thus, here we present a simple, physics-based theoretical model aimed at assessing different escape strategies in terms of their associated ‘energetic cost’ (in work and power) for any given rip current and swimmer’s proficiency level. Many combinations of swimmers and rips are considered, including both idealised and a realistic rip current. Our quantitative results back the common knowledge that swimming against the rip (which is strongly discouraged by lifeguards) is almost universally the worst possible strategy, especially when compared against strategies favoured by experts, such as floating with the current before attempting to swim back to the shore. For a realistic rip, our results suggest that swimming directly against the rip can require several times more power from the swimmer than other strategies advised by lifeguards, thus lending further scientific support to experts’ recommendations. This study may help promote education around the dangers posed by rip currents and how best to address them.

Morpho-dynamic Induced Rip Currents in Klayar Beach, Pacitan, East Java, Indonesia

“…Breaking waves have been believed as a driving mechanism of rip current formation [2,5,12,14]. Waves and tides are predominantly factors influencing coastal morphology and processes [25], and rip current is one of the phenomenons created by the interactions between waves and coastal morphology [8,14,25,28], and often modulated by tides [2,29]. [30] discovered that rip currents vary significantly in occurrence, spacing, and associated nearshore topography, depending on the predominant and the origin of wavebeach conditions.…”

On swimmer's strategies in various currents

“…Both infinity and origin are stable fixed points and there are two saddle fixed points on the y axis. See figure (13).…”

On swimmer’s strategies in various currents

“…To escape a rip, it is dangerous for a swimmer to use the wrong strategies, such as fighting the current. In [13], an 'energetic cost' strategy to escape from a rip current is presented. In this article, different types of strategies for a swimmer who is going to reach a destination are studied.…”