<font color='#0000FF'>Thanks Rob,
When I will buy my breather, yes I will start from shallows and then progress deeper, but I couldn't figer out the above. Altought staying in shallow is hard as with warm water and good wrecks, maybe by then they will invent a depth limiter to the YBOD and if you don't pass eg 30hrs in 20m, if you go deeper it wouldn't work
Maybe I should do a trade mark for it
regards
Pierre