Two of the most common questions I hear asked as people are getting in the sea are, “Which way is the current going? How strong is it?”
Currents are great to know about, and once you work them out, you can use them in your favour if you are planning longer swims. There are many factors that can affect the currents from tides to wind and atmospheric pressure.
In Brighton and Hove, the currents are significantly impacted by the movement of water in and out of the English Channel. Roughly speaking, as the tide is coming in water is flowing in the channel from Lands End to Dover, and the current will be running from West to East. Conversely, as the tide is going out the movement of water flows from East to West. In reality, the currents usually change direction 1 – 2 hours before the tide turns. The period as the currents are on the turn and there is no strong pull in either direction is called slack water. Currents generally accelerate after they turn and are at their strongest three hours after slack water.
Magic Seaweed is a great resource for finding out tide times and trying to work out the currents. I talk more about Magic Seaweed in my blog post, ‘How rough is too rough?’
Tidal range is the distance between the low tide and the high tide on a given day. Tidal range is heavily influenced by the gravitational pull of the moon on the Earth’s oceans.
Spring Tides – Stronger Currents
Spring tides occur during new moon and full moon. This is when the moon’s gravitational pull on the oceans is at its strongest and the tidal range is greater. A larger volume of water flows in and out with every tide, and therefore the currents are stronger.
Neap Tides – Weaker Currents
This is half moon time, when the gravitational effect of the moon on the oceans is weaker. A smaller volume of water flowing in and out of the channel with every tide means the currents are likely to be less strong.
Bear in mind there are many other factors that can affect currents such as wind and atmospheric pressure. It’s good to have a rough guide before you get in but remember the sea can be unpredictable and anything could happen!
A good strategy is to swim out to a buoy, then float for a minute to gauge the direction and speed of the current. If you are doing a there-and-back swim, it is advisable to swim against the current first so it’s easier on the way back when you are more likely to be tired.
When swimming against strong currents, I try not to focus on how far I’m getting and swim for time rather than distance.
For more information on tides and currents, William Thompson at Tidal Compass is the fountain of all knowledge. He runs guided tide walks in Brighton, which I highly recommend.