for all you guys wanting to do the liquid bed install of your transducer (i like that PVC device--very clever), of course water is the easiest to obtain, and retain, but if you find there is a pin-hole leak in your liquid bed, and your water leaks out, no need to freak out and rip it all out and start over. or if you just want something a little more stable, read on. as i elaborated on in my 'everything you ever wanted to know about transducers, but didn't care to ask' post, any liquid or gel will work with ultrasound. (jello works fine as long as there is no air). but, for the purposes here i have a great recommendation for you guys--KY jelly. this gel will not 'run off' like water, or leak out as quickly as water might--if you have that leak i mentioned. the KY is water soluble, its safe for the boat, safe to the environment, is readably available and cheap. it still needs to have no air bubbles, but since its a 'gel', you can press the transducer down into the bed and push out air bubbles. KY also has an antiseptic in it.
for a more professional transducer experience with your liquid bed, you can use actual ultrasound coupling gel--or 'couplant'. you can buy it by the quart or 55 gallon drum for your transducer needs, and--you can use it for, er, 'personal lube' as well. and everyone could use a 55 gallon of sex lube. and the ultragel has antiseptic too.http://www.magnaflux.com/Products/Coupl ... fault.aspx