January 2026

HOW DO TIDES WORK AND AFFECT US?

The tide is created by the gravitational pull of the moon and the sun. We have two high tides and two low tides every day as the earth spins on it’s axis and where we are on the earth faces the moon and sun.

The moon’s gravitational force pulls the water towards it creating a high tide on the side of the earth facing it. Where the water is pulled to is called a tidal bulge.

Because of the balance of forces between the earth and moon spinning around each other it also creates a tidal bulge on the opposite side of the earth as shown in the diagram. So we have a high tide on the side of the earth facing the moon and on the opposite side but on the two sides perpendicular to the side facing the moon we have the low tides - this is where the water is being pulled from.

Things get slightly more complicated when we introduce the Sun into the equation. The Sun is much bigger than the moon but much further away, so the moon’s gravitational pull on the earth is about 2.5 times that of the sun. As a result the gravitational pull of the sun accentuates and diminishes the gravitational force of the moon at different stages of the lunar cycle, making our tides bigger and smaller at different times.

 

When the sun and moon are lined up together (like at a new moon and full moon) their gravitational forces combine and make the tidal bulges either side of the earth bigger. This is because more water is being pulled into the tidal bulge so there is more water at the high tide location and less water at the low tide locations. This is called a spring tide.

 

When the sun and the moon aren’t lined up (like at a half moon) then the sun’s gravitational force pulls away from the tidal bulge meaning less water gets pulled into the high tide locations. This means we have less water at the high tide locations and more water at the low tide locations, in what is called neap tides.

In reality this means that our tides go through a 28 day cycle along with the moon: At the new moon in the north east we have a high tide measuring about 5.1 metres and a low tide measuring 0.9m. As the moon moves round to and becomes a half moon our high tide can be as little as 3.9m and our low tide as high as 2.2m. Again as the moon moves round to full moon we have a high tide of at least 5m and a low of just under 1m and again as we move to another half moon we get a high of just under 4m and a low of just over 2m. (In other locations in the UK this tidal range can drop to as little as between 1 to 4 metres in range and increase to 1 to 11 metres in range. This is because the land masses on the earth get in the way of the tidal bulge moving and so we have locations with much bigger tides and some locations with no tide at all.)

This means at certain times we have either much more water and much less water at our surf spots meaning that the depth of the beaches we’re at will change and as a result so will the way our waves break. Similarly the amount of water moving changes and the effect of these tidal currents on our surf spots are unique to the bathymetry (shape of the sea floor) of each place and can change the surf. 

 

It’s also important to note that our tides don’t move evenly in and out but increase and decrease in the speed of flow. It takes approximately 6 hours to move from low tide to high tide and then another 6 hours to move from high tide to low tide. In these 6 hour periods the tide flows at different rates:

In the first hour 1/12 of the water moves, the 2nd hour 2 twelfths, the 3rd hour 3 twelfths, 4th hour 3 twelfths, 5th hour 2 twelfths and 6th hour is 1 twelfth again. So half the water moves in the middle two hours in between low and high tide, and only 1 sixth of the water moves in the first and last hours. So this means the hour either side of low or high tide not much water moves at all, then it all moves in those middle hours.