When looking at marine electronics, you'll see a JISx listing. This refers to the level of waterproofing.
Here is a definition of the scale:
JIS SCALE
The Japan Industrial Standards (JIS) for water resistance uses a "0" to "8" scale to define the level of water ingress protection built into each product. If the product was tested in compliance with this standard it is usually listed on the product spec sheet. The various JIS classes are defined below.
JIS "0" No special protection
JIS "1" Vertically dripping water shall have no harmful effect (Drip resistant 1)
JIS "2" Dripping water at an angle up to 15 degrees from vertical shall have no harmful effect (Drip resistant 2)
JIS "3" Falling rain at an angle up to 60 degrees from vertical shall have no harmful effect (Rain resistant)
JIS "4" Splashing water from any direction shall have no harmful effect (Splash resistant)
JIS "5" Direct jetting water from any direction shall have no harmful effect (Jet resistant)
JIS "6" Direct jetting water from any direction shall not enter the enclosure (Water tight)
JIS "7" Water shall not enter the enclosure when it is immersed in water under defined conditions - 1 meter of water for 30 minutes(Immersion resistant)
JIS "8" The equipment is usable for continuous submersion in water under specified pressure (Submersible)
Waterproof Rating Scale
Waterproof Rating Scale
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