Diving and snorkeling in Sali

How we work out the diving rating

We score every moment of the day, every 10 minutes, from 0 to 10, with simple fixed rules:

• Swell: takes points away based on its height and period (a 10 s swell weighs 50% more than a 6 s one, because it reaches deeper and moves the bottom): nothing under 1.6 ft, up to 6.5 points from 9.8 ft. Surface waves count for getting in and out; we take the worse of the two.
• Wind: takes points away from force 4, about 12 mph (1 point), up to 6 points in a gale; half a point more when it blows offshore, because it pushes surface swimmers away from shore.
• Current: Météo-France's model current takes points away from half a knot (1 point) up to 6 points from 2 knots.
• Slack water: where we show the tide, up to 3 points come off when the water rises or falls fast (mid-tide, especially on spring tides) and none at slack, around each high and low tide.
• Light: half a point more with the sun high (3 hours either side of solar noon), 1.5 less at twilight and 3 less at night. Thunderstorms take away 5 and heavy rain 1.
• Likely visibility: good, fair or poor from the swell of the previous 48 hours, the rain of the previous 72 and the wind of the previous 24. Fair takes 1 point off the day's rating and poor, 2.
• Day's rating: the average of the best window (the stretch of 40 minutes to 3 hours with the best conditions), adjusted for likely visibility.
• Wetsuit, by water temperature: below 50 °F, drysuit; from 50 °F, 7 mm semi-dry; from 57 °F, 7 mm wetsuit; from 64 °F, 5 mm; from 72 °F, 3 mm; from 79 °F, shorty or rash guard.

Today: the best window scores 10 out of 10 and visibility is likely good, so it takes nothing off.

It's an estimate from the swell, rain and wind of the previous days, not a measurement: real visibility also depends on the bottom, plankton and nearby rivers.

It is a guide built from models, not a guarantee: every site has its own currents and bottom. Look at the water when you get there and ask the dive shop.