The challenge I've had is the same, the data format that a lot of these sources provide is in "academic" formats like GRIB, NetCDF etc.. and I've spent a not-insignificant amount of time trying to work through all these formats and what they represent.
I want to integrate regular wave forecasts in the next month, but I am unaware of something that can improve dive visibility.
Anecdotally I find it's best when the wind is offshore and there is low tidal movement. But there are other factors at play, such as rainfall, etc..
This is one source I found (for wave height): https://www.aviso.altimetry.fr/en/data/products.html, however it was not clear on the website whether it was paid or not.
Another one I had a poke around with: https://www.ecmwf.int/en/forecasts/datasets/wmo-essential (trying to read Grib2)