What decides dive visibility, and how to estimate it before you go

Rain, wind, swell and the kind of site matter more than most divers expect.

Underwater visibility changes with recent weather as much as with the day you dive. Knowing the main drivers helps you choose a site and a time.

The main drivers

• Rain and runoff. Heavy rain washes sediment into the water, and it can take days to settle. Bays, river mouths, rivers and lakes are hit hardest and clear slowly.
• Wind. Days of strong wind stir the water and build waves, especially on exposed coasts.
• Swell. Short, steep chop usually hurts visibility more than long, gentle swell of the same height.
• Tides and currents. Water moving in and out of an estuary or lagoon can carry cloudy water to the site, or clear it.
• Type of site. An open-sea reef, a bay, a river and a cenote respond very differently. Caves and cenotes, for example, are largely independent of recent rain.

How GoDrift estimates it

For any site you search or save, GoDrift fetches recent and forecast weather and sea conditions and turns them into an index from 0 to 100, labelled Good, Fair or Poor. The index drops with recent rain (weighted more heavily for the last day), the average and gusts of wind over the previous three days, and swell height and period. It is adjusted for the type of site, so a river is judged by rain and a cenote is treated as constant.

Each estimate shows a range that widens for days further out, and the best window of the day within daylight hours. It also shows hourly weather, water temperature, currents and tide times for the site.

GoDrift gets weather data from Open-Meteo, using only the site's coordinates rounded to two decimals. Weather data by Open-Meteo.com (CC BY 4.0).

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