IP stands for Ingress Protection, and is a rating of how resistant the radio equipment is to water and dust ingress.
Therefore a high IP rating is important in a Marine environment.
The IP rating is especially important for sea going yachts, as the corrosive effects of salty sea air can penetrate the casing of radios with too low an IP rating.
The effects of corrosion on a radio with too low an IP rating, will be premature failure of the radio equipment. This is often because the PCB ( Printed Circuit Board) inside the radio, gets attacked and corroded.
PCB corrosion can also occur within environments, such as Indoor Swimming Pools, where a high Chlorine environment may be present.
An IP67 or IP68 radio, such as the Entel DX series, can be dropped into water with no ill effect.
Yachts battery rooms need not only a radio with a high IP rating, but also ATEX (Intrinsically safe) protection, due to the potentially explosive environment (ask us for specialist advice).
Of course not every yacht needs radios with high IP rating, and for cabin use, something like the excellent Hytera PD405 would be ideal.