Why is Sea State So Important?

Why is Sea State So Important?

November 23, 2018 Sailing news 0

Experienced boating people know how to read the sea state at a glance, in doing so they know to recognize changes as they occur. Just as the wind on your face can tell you if the wind has veered, sea state can tell you what is happening on the surface of the water i.e. flat calm becomes choppy, knowing there is a change occurring will tell skippers what they need to do, if anything. Clearly, the onset of heavy weather may mean a change of course or a return to the Marina.

Marineforecaster’s Weather Forecast

Sea state is the general condition of the expanse of water that you are on, ocean sailing, coastal boating, inland sea and lake sailing and so on. Sea state analysis means considering the overall condition of the surface such as waves height changes, swell and usually ties in with wind patterns. However, it is possible to have a very large sea with light winds.

The dangers are obvious of being out in a sea too large for your boat and your level of ability. The state of the sea can also have a dramatic effect on the consumption of fuel putting power boats and cruisers at potential risk of running out of fuel, if a motor is having to work harder it will burn more fuel.

The state of the sea is described using the Douglas scale, like the Beaufort scale for wind strength.

There are actually two scales, both ranging from 0 to 9; one to measure swell  (longerflatter waves that travel over oceans) and one to measure the wind sea (wavescaused by the wind in the local area). The wind sea is the scale more commonlyused in coastal areas.

Wind Sea Scale

Degree Height (m) Height (ft) Description
0 no wave Calm (Glassy)
1 0–0.10 0.00–0.33 Calm (rippled)
2 0.10–0.50 0.33–1.64 Smooth
3 0.50–1.25 1.6–4.1 Slight
4 1.25–2.50 4.1–8.2 Moderate
5 2.50–4.00 8.2–13.1 Rough
6 4.00–6.00 13.1–19.7 Very rough
7 6.00–9.00 19.7–29.5 High
8 9.00–14.00 29.5–45.9 Very high
9 14.00+ 45.9+ Phenomenal


Degrees Description
0 No swell
1 Very Low (short or average and low wave)
2 Low (long and low wave)
3 Light (short and moderate wave)
4 Moderate (average and moderate wave)
5 Moderate rough (long and moderate wave)
6 Rough (short and high wave)
7 High (average and high wave)
8 Very high (long and high wave)
9 Confused (wavelength and height indefinable)

Keeping an eye on sea state, wind state and general weather conditions are essential skills for skippers for whom sailing should be fun and exciting – for the right reasons. Experienced skippers and crews will challenge themselves against the elements, but they will also know at what stage they are taking undue risks.

All would-be boating people are strongly advised to undertake professionally recognised sail training before heading out of the Marina, harbour or cove.Taking ill-advised risks is to put your own life at risk and your crew, and the people who will put themselves in harms way to save your neck.

Enjoy sailing, sail safe.


Author: R. langley