What type depth finder do you have?
Yes, a PO had tried that in my boat too. Its an alternative to the epoxy method but, at least in my case, can be messy. It was a poorly done install and all the oil ran out. Water can be used too. The epoxy makes a neat job of it and lets face it, how often do you need to remove the transcucer when its not being exposed to the elements anyway?
The main reason I went epoxy instead of thru-hull is simply because the boat was already afloat. I really have no qualms with drilling holes in my boat. God knows my wife would tell you thats all I do!