Understanding Tide Tables

Understanding Tide Tables is something that is very important for some of the Coasteering venues that we use in Northern Ireland and Ireland. Ballintoy is brilliant because we can coasteer there no matter what the tide or sea state is like – it can be really rough and it’s great and it can be as flat as a pancake and it’s great. Other venues need certain conditions to make them safe and that’s when reading a tide table is crucial…

First off you need to know where you can find tide tables. There are loads of sites that offer them but we really like the clean interface offered by the BBC site.

Select what area you need and then you will see 3 columns on the left of the graph. These show:

• High and low tides
• The times
• The height of the tide

This is pretty straightforward, the tide will be at it’s highest at 0320 and then again at 1505. Note, although it might appear that tides work it in a 6 hour cycle this is not actually the case.

The height of the tide also varies and this is to do with the stage of the moon and it’s gravitational pull. When we have a new moon or full moon we will experience higher high tides and lower low tides. See next diagram:

If you compare both graphs you will notice that the height difference is much more dramatic in the second graph – that’s because this one if for a full moon.

Another important thing to know is that for a period of time at high tide and low tide there is very little gravitational pull and therefore the sea will be relatively still. These slack tides can last 1-3 hours split on either side of the actual low or high tide time.

It must be remembered that there are many other factors that determine whether it is safe to go in the sea. Local knowledge is a huge factor and one which should never be overlooked.

We will be adding some more information on “understanding the sea” over the coming weeks but if you have a question please get in touch.