While I do enjoy getting spooked by the local critters emerging out of cloudy 2m viz… it is nice knowing when the water is putting its beautiful reefs on full display.
Water visibility is mainly a function of swell, wind, and recent rain fall. The direction & magnitude of those factors, plus a dive site’s local geography all contribute.
Waves can disturb the sediments on the sea bottom. This causes sand and other particles to become suspended in the water column, thus decreasing visibility.
Wind can create surface waves as well as influence local currents. This affects the visibility similar to swell - causing more particles to float in the water column.
Heavy rains wash sediments, organic compounds, and pollution from the land into the sea. The runoff itself decreases visibility greatly. Additionally, the matter in the runoff encourage algae to grow faster - further decreasing the viz.
Headlands and other geographic features can protect a dive site from swells and winds. However, when the swell is extremely large, it can wrap & bend around headlands - affecting even the most protected sites.
If a dive site is close to a river, near an urban area, or at the end of a valley – it will be affected by runoff more severely.
Dive sites that are extremely protected will take longer to be affected by changes in these conditions. However, it can also take them longer to improve again once conditions turn around.
When all the visibility factors are improving or degrading together, it can be pretty easy to predict the viz using local weather reports. If it has been sunny, flat, and dry for a week – then it’s probably going to be pretty great out there!
Things get tricky when the factors move in opposite directions though.
The viz app was created to circumvent the difficulty of forecasting and give divers a “live” view of the water conditions instead! By enabling divers to share the viz with each other, it’s possible to have a very accurate report for each dive site.
I believe that technology should encourage participation instead of just automating away the things that give us joy! Hopefully next time you dive, you’ll send your log along and help out everyone else (or at least give them FOMO if the viz was great during your “lunch break” dive).
