[Fondueset]

I have done the types of dives Sedate describes - mostly one day in an inland lake here. I could not see so I simply went as deep as I possibly could before hitting bottom. Water came out of my sinuses for a couple of days - but this was very dangerous due to the risk of infection - freshwater!!
This is the first concern that comes to my mind though I have not researched it - because I do not dive that way now.
I would urge caution, training, education and a very competent buddy.

Maybe talk with Sebastien Murat?