Hi,
Welcome, our last trip was to Berlin for Christmas 2019. Magical! No diving, though.
This board is very permissive, as far as I know commercial posts are permitted without prior approval.
If you manage to put together a portal for dive site information, I think that would be great. There's a lot of information that I would like to have!
Long term info:
Depth
Seasonal water temperatures
Seasonal weather
Access (transport, parking, entry)
Local risks: current, animal, boat traffic
Location of closest chamber
Short term info:
Wave height - Locally I use this:
Monterey Bay Swell Forecasts The ones with broad national or international coverage seem oriented toward surfers
Visibility - often found on forums such as this one. Very hard to find unless you call a shop or know someone. A "viz forecast" would be huge!
Local surface weather forecast - In the U.S. I use weather.gov but elsewhere Intellicast
Tide forecast
Good luck with your research. That's not my area but I do enjoy noodling in UX.