Tides, Rip Currents, and Safe Swimming

May 20, 2021 // Article by: Jen D’Iorio

As we progress through the Spring, each passing day brings us one step closer to beach season. For many, the summertime marks countless days spent relaxing at the beach. Laying in the sun, building a sand castle, and swimming in the water are some pastimes enjoyed by various beachgoers. However, safety precautions cannot be forgotten while enjoying a day at the beach, especially when it comes to floating in the ocean or riding some waves. Tides and rip currents are two factors that have an effect on swimmer's safety, and will be discussed further below.

Tides:

First, let's talk about what exactly tides are and how they form. A tide can be defined as the alternating rise and fall of the ocean's waters (though tides can occur in some rivers and lakes, too). This rise and fall is caused by the gravitational pull of the Moon on Earth, as well as Earth's rotational force. High tide, which is when water advances to its farthest extent on the shoreline, occurs on the side of Earth closest to the moon. Since this side of Earth most strongly experiences the Moon's gravitational pull, the Earth's surface bulges and water's rise, forming a high tide. However, high tides also form on the side of Earth directly opposite/facing away from the Moon. Here, the rotational force of Earth is strongest while the Moon's gravitational force is weakest, causing seas to rise as well. Elsewhere on Earth, the ocean recedes to its farthest extent on the shoreline, therefore creating low tides.

Depiction of Earth's High and Low Tides, Courtesy of National Geographic

The sun plays a minor role in the formation of tides, too. When the Earth, Moon, and Sun line up (which occurs at a full moon or new moon) more extreme high and low tides can occur, which happens about every two weeks across our oceans (known as spring or king tides).

Depiction of Earth's Highest and Lowest Tides, Courtesy of National Geographic

Typically, shorelines experience two high tides and two low tides within a period just over 24 hours.  This is how long it takes the Moon to completely rotate once around the Earth. The height of tides is largely affected by the shoreline's physical shape and geographic features. 

When going to the beach this summer, it is important to take into account the times safest for swimming and enjoying the water with respect to the ocean's tides. Tidal currents accompany tides, which are the horizontal movement of water to and from the coast. Water moves towads the coast in a flood tidal current during a high tide, while water moves away from the coast in an ebb tidal current during a low tide. Flood and ebb currents are the strongest at or around the peak of high or low tide, making this the most difficult and dangerous time for beachgoers to swim in the water (especially during flood tide). Meanwhile, the water is safest when tidal currents are the weakest, or during a slack tide, which happens in the hour preceding or following a high or low tide. During this time, the water moves very little, and waves are calmer and less dangerous. Current tide info for various locations along the East Coast can be found here to provide for safe beachgoing this summer.

Rip Currents:

Rip currents are an additional ocean hazard that can threaten the safety of those in the water. Rip currents are powerful, narrow channels of fast-moving water that move directly away from the shore and extend from close to the shoreline through the surf and past the breaking waves. Strong rip currents can actually travel at speeds faster than an Olympic swimmer! Rip currents are dangerous because they pull swimmers farther away from the shore. Unfortunately, there are around 100 rip current fatalties across the country each year, with around 80% of all ocean rescues being rip current related. 

When going to the beach, it is extremely important to have knowledge on what rip currents look like and how to spot them in the water. It is easiest to spot rip currents from an elevated position overlooking the beach, as they are typically found in areas where waves are not breaking. Additionally, rip currents may look darker, muddy, or choppier than the surrounding ocean waters.

Depiction of a rip current found on an Atlantic Ocean Beach, Courtesy of the National Weather Service

Checking water conditions for the day before heading to the beach by looking at a local beach forecast  for your area is extremely important for swimmer safety. Just because the weather is nice does not mean there will not be rip currents, as rips often form on calm, sunny days. Additionally, always be sure to swim at a beach with lifeguards, as the chances of drowning at a beach with lifeguards are 1 in 18 million. Be sure to know what warning flags mean when arriving to the beach. A green flag means water conditions are safe for swimmers, while other flag colors mean conditions are unsafe for swimming.

Different Beach Warning Flags, Courtesy of njsurfschool.com 

Finally, be sure to know how to escape rip currents just in case you accidentally become caught in one. The biggest rule is do NOT try and swim direcly to the shore while in the rip, as the rips speed and force out to sea will only use up your energy. Instead, swim along the shoreline until you can escape from the current's pull, then swim at angle away from the current and toward the shore.

Courtesy of the National Weather Service

Sources:

National Geographic: https://www.nationalgeographic.org/encyclopedia/tide/

Swim Guide: https://www.theswimguide.org/2020/02/13/what-tide-is-best-for-your-favourite-water-activity/

National Weather Service: https://www.weather.gov/safety/ripcurrent

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