Marine electronics encompasses electronic devices and computers used aboard ships and boats, for marine navigation, Safety of Life at Sea, fisheries monitoring surveillance and control, etc., It may be commercial, recreational, or military, but military equipment under this category will be dual-use, such as a navigational radar used both on civilian and military vessels. Sonar technology will be oceanographic, fishfinding, etc., rather than, for example, anti-submarine warfare.
In this context, navigation includes not just position finding equipment such as GPS and LORAN, but equipment that integrates them, such as Electronic Charting Systems and chartplotters. It also considers devices that control the vessel's course, such as autopilots and steering gear.
Safety and security
The starting point here is the requirements of the Safety of Life at Sea convention, with supplementary equipment used optionally or by local requirements. Security devices, ranging from anti-piracy to alarms on the fuel tanks of boats tied up in marinas, also go here, as do such things as fire and high water sensors.
This includes onboard sensors as well as receivers for weather broadcasts.
Resource monitoring surveillance and control
While the primary example is fisheries monitoring surveillance and control, it certainly is reasonable to consider such things as seabed mining, oil drilling, etc.
Radios in the HF and VHF marine bands begin the category, but also extend to maritime satellite communications, boosters for cellular radio, and other services operated from vessels.