Understanding tides and how they affect your vessel is critical to making any passage short or long. Get it right and you can have a slick, quick, fun journey to your destination, an easy park in the marina of your choice, making that dinner reservation and getting to the pub before closing time. In my experience this also has the vicarious benefit of a happy and contented crew.
Getting it wrong and misunderstanding tides can mean a long hard slog to your destination, hairy parking options and having to cook that old Fray Bentos pie that has been in the back of the galley cupboard for years. This also may have the vicarious benefit of weeding out the less hardy members of your crew but please do bear in mind this will most likely be family and friends.
Getting it right is what we are looking at in this article. Do not worry, I am not going to wax lyrically about moon cycles and the influences celestial bodies have on the earth. This may be controversial, but I would rather give some insight on the tools of the trade and how to use them to understand tides, rather than rehash what you may have learnt in school or on sailing theory courses.
Your first stop to understanding tides could most likely be tide tables in a hard copy Almanac like Reeds with which most will be familiar and can be found on most school/charter boats and training versions of which are used in theory classes. These are quite often used with a Tidal Atlas whether that be the ones found in Almanacs, Admiralty publications or regional local versions. Your other option is an App (used on your phone or tablet), of which there are many. My personal favourites are Boatie and Imray Tides Planner. Navionics also now provides tidal data and tidal streams.
The one common denominator is that (unless you are abroad), they draw data from the same well, the UK Hydrographic Office. The ease of access to tidal information has changed massively but just like weather apps, I would recommend you make sure you are drawing from a reputable source. You can get Admiralty tidal information for free from Easy Tide https://easytide.admiralty.co.uk
The added value from good apps is that they can provide tidal streams information and also secondary port information which can take the some of the pencil work out of your navigation and planning.
So how should we use all this information to better understand tides? Well, firstly and as already alluded to, it is useful to know in which direction the tide is flowing for you proposed journey. If your local and familiar with the Solent, you will know that the tide floods west about an hour before high water, and ebbs east about an hour before low water. Local knowledge is great, but if you are not local or familiar with where you are going, you are going to have to hit the almanacs or Apps to find tide times and a tidal streams atlas to determine direction.
Spring vs neap tides
When you look at your tide tables, they will also tell you whether you are at “Springs or Neaps,” or somewhere in between. This is where the range between High and Low waters changes over the lunar month. When this range is at its greatest the tides are referred to as ‘Spring tides’ and when the range is at its smallest the tides are ‘Neap tides’.
In the simplest terms this means that there will be more fast water flowing during Spring tides than Neaps making it harder for example to sail up tide at this time. Conversely using the tide to your advantage, you can add knots of speed to your passage. Spring tides will also mean there will be a lot more water flowing through the marinas at this time making parking in your berth a little bit trickier. The last area for consideration with spring tides is there will be significantly less depth at low water over hazards and obstacles making good navigation all the more critical.
Take a look at these tidal curves and the differences between springs and neaps.
You can clearly see the difference between spring vs neap tides. Springs here has a range of 3.6m whereas Neaps has only 1.8m, that is half as much water flowing as there is at Spring tide. You can also see the gradients of the Spring tide are much steeper and therefore much stronger than the Neap tide. Imagine trying to get through a tidal gate like the Needles with a Spring tide against you. Not fun. So, you now have a clear image of what you could be contending with.
If you really want to know when spring tides or neap tides are occurring, do not rely on the moon! Check your almanac because in certain areas springs can be anything up to 4 days after a new or full moon and a lot of tidal prediction also come down to the geographic location of the tidal station in question. There are parts of the world where Springs appear to occur before the new or full moon phases but are actually 11-14 days after the previous moons.
The other often vaunted theory is that HW springs always occurs at 0000 and 1200 which is not strictly true. Plymouth is around 0700; London around 1600; Greenock around 1330. This is because the moon and the sun are precisely in phase. The image below is from Southampton, and you can see where this theory comes from but it’s never 0000 or 1200 on the dot and there can be up to an hour’s difference. Remember these are very coarse times with broad variations.
Coming back to the tidal curves, these are really useful for planning your port entries and berthing arrangements. On The Hamble River where I live and, on the Itchen River, where I often work are both tidal and the tide absolutely spooshes* through both, particularly around LW and HW Springs. I always look at the tidal curve when out and about on boats and will generally plandepartures and arrivals around HW and LW if I can.
The other element you to look for to better understand tides for boating is where the tide stands or is slack (is not moving). As you can see on these tidal curves for Southampton there are two very distinct “stands” where the incoming tide slows down and is almost slack, which can help planning when to leave or depart a marina. (See the crosshairs and little yacht on the graphics).
Neap tides also stand, but it is not so pronounced or as prolonged as Springs, but they still offer easier berthing opportunities. The stands will of course increase and decrease in between Spring and Neap tides.
Last but not least is the low water stand. This in my experience you have to be on time for. As you can see you there is not as big a window of opportunity as you may have with the mid flood and high water stands and quite often either side of the stand the water can rip** in and out quite rapidly as it changes from ebb to flood or vice versa.
So as per my last article, it always pays to plan your passages carefully and take full account of what the tide is doing at each stage of your journey. Use the tides to you advantage and try not to be caught out. If for whatever reason you do end up having to work against a foul tide, make sure your crew are aware and understand. For longer passages it can be well worth putting in somewhere or anchoring and waiting for the tide to change in your favour.
Make sure you boat handling skills are up to speed as there may be a time where you need to berth in a running tide, but it’s not recommended. Ferry gliding is an essential skill to have and needs to be practiced. Build and be confident in your skills before attempting any manoeuvres down tide. Marinas are remarkably good these days at making sure they put you into up tide berths, it’s in their interests after all. If you are ever offered a down tide berth, feel free to turn it down and ask for one up tide. Always park into the tide.
As one of my instructors says, “Tide is King, I repeat, Tide is King! If you’re thinking of parking a boat with the tide, think again!”
Alex Guerandel
Ocean Yachtmaster & Cruising Instructor
* my technical term for a lot of liquid moving quickly through a small space
** similarly meaning to spooshing
