Speedtech Depthmate Portable Sounder SM-5A

Find deep water easily from your dinghy. This unique pocket-sized depth sounder is very accurate and of very high quality. It is useful for boating, fishing, scuba diving, coastal survey, and scientific work.
Reads to the nearest tenth in feet or meters, through a solid hull, inflatable bottom, or black ice. This is an extremely accurate unit when used properly.
Simply put the head in the water, or against the solid hull of a boat. (Sonar will not read through air.)

Models are available with or without an external transducer.
Using the SM-5A (model with transducer) improves accuracy at a distance and will be necessary whenever the SM-5 depthsounder alone can not reach the water. With the transducer at the end of a 12-foot wire, the unit can be used from boats, mounted inside or outside of the hull, or on a pole or boathook. The transducer fitting is waterproof, however, it is not for underwater use and cannot be submerged.

Specifications:

Frequency - 200kHz with 24° beam angle
Depth range from 2 to 260 feet (0.6 - 79 meters)
Power - Standard 9V dry cell battery (provides 500 x 10 second readings)
Dimensions - 7.7" x 1.7" (198 x 42mm)
Each reading is backlit and stays displayed for ten seconds
Note: The SM-5 can be converted to an SM-5A with the purchase of the EC-5A + Transducer. Depthsounders manufactured prior to 2001 cannot be converted.