As Martin said the trasnsducer needs to be covered in water to work at is best so make up a small tub/box, epoxy the t/ducer into tub/box, fix tub/box to lower skin, fill tub with water and fit a water tight lid with the wires sealed with silicon or grease.
Make sure the transducer is level with the sea water otherwise you will not see straight down
Job done
Coddy