If you are in europe and are looking for professional equipment:
www.maritimerobotics.com/ These guys thier Otto model is great for mapping small ponds and such.
Data wise why dont you just slap it straight into your leica software? (cyclone?)
I suppose if you want to keep it really simple you could use a lowrance unit, log the data, import the .sl(3) file in RM and export .csv. Take the .csv apart and import that into your leica software.