of rubber or neoprene which is tightly fitted in the aperture 460 the arrangement of fig5 provides for easy access to the interior of the casing 420 fig6 shows another alternative sealing member 500 for sealing the top of a casing 520 the casing 520 is substantially similar to the casing 120 or the casing 20 and has an outer surface 544 having an outer diameter and has an inner surface 548 having an inner diameter in the embodiment of fig6 the outer surface 544 has threads 550 proximate the top of the casing 520 the sealing member 500 includes a cap or piece 552 having an inner surface 554 with threads 556 that are complementary to the threads 550 so the cap 552 threadingly mates with the top of the casing 520 preferably teflon tape or thread sealant is placed between the cap 552 and the outer surface 544 the transducer cable fig1 embodiment or the transducer cable and tube fig2 embodiment pass through the sealing member 500 so as not to provide a path for air to pass into the casing for example the cable or cable and tube pass through an aperture in the sealing member 500 and a seal is then provided such as by using epoxy caulk a one holed stopper a compression fitting etc in one embodiment the cable or cable and tube pass through a central aperture 560 in the cap 552 in the illustrated embodiment the cable or cable and tube pass through an aperture in a one holed stopper 566 e g formed of rubber or neoprene which is tightly fitted in the aperture.