Depth transducers

From our buying guide

Raymarine's general guidance is 200 kHz for water under about 60 m (200 ft) and 50 kHz for deep water. In-hull transducers avoid a hole, but lose performance and need a solid fiberglass bottom.

Check before you buy:

• The housing suits your hull. Airmar and Raymarine rule out plastic on a wood hull and bronze on a metal one.
• It connects to your display, since an analog transducer needs an interface.
• A through-hull will be fitted to the maker's guide. Garmin says its own should be installed by a qualified marine installer.