​What are tides and how do they work? A guide from the RNLI

March 19, 2021

You’re planning a swim and you’re always advised to check the tides before you go, so what does this actually mean and how can how you use this knowledge to your advantage?

It’s important to understand that water is always moving, it’s caused by the gravitational pull of the moon and the sun.

The tide typically ranges from high tide to low tide and back to high tide in just over a 12-hour period, hence the tide times change each day.

Types of tides – Spring Tide and Neap Tide

As mentioned above the tide is impacted by the moon, so as the phases of the moon change throughout the month so will the range of the tides.

  • Spring tides have greater depth range between high and low water, so at high tide the water comes in further up the beach. Spring Tides create a potential for a greater force on beaches when tide is ebbing or flooding. These occur during a full / new moon – earth, moon and sun in a line
  • Neap tides have less variation, so at high tide the water won't come in as far. These occur during the half moon – earth, moon and sun at right angles

Typically there are 2 neap and 2 spring tides in a month.

Knowing the tides can allow you to make better decisions on where you go for your swim, some locations are only suitable for swimming at during fuller tides.

Also, depending on the weather, you may not want such a long walk down the beach before reaching the sea.

Where to get tidal information

There are a multitude of websites and mobile apps where you can easily get the tide times for your location. They may also be printed and posted on local noticeboards, sailing clubs or in local papers.

Some examples – Magic Seaweed, Ireland Tides - Tides Near Me, Irish Sailing Association, www.safetyonthewater.gov.ie.

Using tidal information to make your decision

Knowing the tide times allows you to better plan when and where to go for your swim, helping to make it a safer more enjoyable experience.

The three tidal aspects you should consider before swimming are:

Height of tide – What level is the sea going to be at your swimming location? Are there visible and accessible entry and exit points to the water. Are there any exposed rocks or under water hazards you need to be aware of? Will you have a long walk from the beach to reach the sea?

Direction of flow – Which way is the water flowing? A flood tide refers to the tide coming in, an ebb tide refers to the tide going out. Depending on the direction of the flow you can get pulled or pushed in the direction that the current is flowing.

Speed of flow – How fast the water is flowing? The fastest moving water is typically 3-4 hours after a low or high tide. Will you get dragged in a certain direction, are you swimming with or against the tide? Are you planning to get in and out from the same point?

Look out for signs of the flow of the water, such as the flow of the tide past a buoy or a pot marker, rock, or other fixed object in the water. Alternatively look at floating objects such as seabirds and seaweed etc. Which way are they drifting and how fast?

Demystifying Rip Currents

Rips are strong currents running out to sea, which can quickly drag people and debris away from the shallows of the shoreline and out to deeper water.

They tend to flow at 1–2mph but can reach 4–5mph, which is faster than an Olympic swimmer.

Rips are especially powerful in larger surf, but never underestimate the power of any water. They are also found around river mouths, estuaries and man-made structures like piers and groynes

How to spot and avoid a Rip

Rip currents can be difficult to spot, but are sometimes identified by a channel of churning, choppy water on the sea's surface.

Sometimes the water can appear darker in a rip. On other occasions, if there are breaks in the waves on the beach, the area where there are no waves may be a rip.

Even the most experienced beachgoers can be caught out by rips, so don’t be afraid to ask lifeguards for advice. They will show you how you can identify and avoid rips.

The best way to avoid rips is to choose a lifeguarded beach and always swim between the red and yellow flags, which have been marked based on where is safer to swim in the current conditions.

This also helps you to be spotted more easily, should something go wrong.

What to do if you get caught in a Rip

- Don’t try to swim against it, because you will get exhausted.

- If you can stand, wade don’t swim.

- If you can, swim parallel to the shore until free of the rip and then head for shore. If you can’t, remember the FLOAT message – lie on your back and control your breathing.

- If you are in difficulty, always raise your hand and shout for help.

This advice is brought to you by the RNLI, whose volunteer lifeboat crews save lives at sea 365 days a year.

rnli.org