Nicky,

Like the guy said in "Down Periscope" "It'll go all the way to the bottom" However, for R/C purposes usually 6 feet is about as deep as you want to go. Depends greatly on the type of water you are in. Some have better radio transmittability(?) abilities than others. Other variables include your transmitter batteries, receiver batteries, antenna length, etc. I did speak to Chris Cloke (owner of Sheerline subs) about a month ago and he told me he had one of his boats down 11 feet and was able to bring it back up. Said it took him a while though.

Pete