5.3 Choosing when to make the crossing
The first decision to make when planning a crossing is to choose when to go. The tidal streams that affect the crossing will make the journey much easier at some times than others. Often, tidal stream atlases can be a good source of information to gain the overview needed to begin thinking about this.Factors to consider include:
Whether it is springs, neaps or in between. The effects of the tide will be less around neaps, increasing margins for errors.
When the tide will turn. For crossing that cross the tide (e.g. most crossings from the UK mainland to Ireland), it makes sense to choose slack water in the middle of the crossing so that the effects of the tide cancel over the crossing and no net effort is put into paddling against the tide. For crossings in the direction of the tide (e.g. Ilfracombe to Lundy), it makes sense to cross when the tide will assist your passage.
Areas of overfalls. For some crossings, it will be important to avoid areas of overfalls and races when the tide is strong. For this reason, you might choose to arrive at a destination headland at slack water.
Periods of daylight. Some otherwise perfect time windows may be in the middle of the night, which is obviously not ideal. It may well be better to start the crossing in the dark than be chasing the last light at the end of the crossing.
It is possible that you will need to make some compromises. In some areas, picking neap tides will mean that the only usable slack water is in the middle of the night. Clearly, it’s not possible to time slack water for both the middle of your crossing and your arrival at a headland.
Obviously, the weather will determine whether it’s sensible to undertake the crossing - most people will only contemplate a multi-hour crossing in settled conditions. It may turn out that the day you pick has poor weather, and you’ll have to leave the crossing to another opportunity. Tidal conditions tend to be similar from one day to the next, so you may be able to pick the best day from 3 or 4 that all have a sensible tidal setup.
Here’s an extract from a tidal stream atlas showing the area between Burrow Head and the Point of Ayre
It appears that slack water is around high water Liverpool and HW Liverpool +6:30 (i.e. LW Liverpool). Around high water Liverpool, it looks like the tidal stream at Point of Ayre turns a little ahead of the main stream.
The distance of the crossing is around 15 nautical miles, so we expect it to take around 5 hours. We’ll arrange for the middle hour of the crossing to be around slack water at HW Liverpool (or LW ), so that we start around 2 and a half hours before high water or low water at Liverpool and finish 2 and a half hours after. So, we’re looking for days with a small tidal range and HW or LW near the middle of the day.
We’d like to do the crossing in August 2025. Here’s a tide table for that month:
The smallest tidal range of the month is August 4th. On this day, we might use the low water slack at 14:12 (accounting for BST). Similar conditions, with slightly larger tidal ranges occur on the 18th and 19th. These days look optimal from a tidal perspective.
However, to make some of the principles clearer in this example, we’ll choose a day with a rather larger tidal range - the 9th August. On this day, high water is at 12:07 BST and the tidal range is 7 metres. For simplicity, we’ll assume high water at 12:00. The timings for the crossing are thus:
| Time relative to HW Liverpool | Time (BST) | Expected tidal stream |
|---|---|---|
| -2 (-2:30 to -1:30) | 09:30-10:30 | East-going, strong |
| -1 (-1:30 to -0:30) | 10:30-11:30 | East-going |
| 0 (-0:30 to +0:30) | 11:30-12:30 | Slack |
| +1 (+0:30 to +1:30) | 12:30-13:30 | West-going |
| +2 (+1:20 to +2:30) | 13:30-14:30 | West-going, strong |
We’ll update this table as we gather more information about the tidal streams.
This plan involves us arriving at Point of Ayre with a strong west-going tide running. We may wish to check how severe the overfalls are likely to be at the Point, and devise a plan that enables us to land to the west of the point should we get swept in this direction.