The NEMA Publibication mentioned by mjl2023 is quite excellent as applied to fresh water incidents or sweet water as it is sometimes called.
Exposure to salt water splashing or spray with only surface contact can be easily resolved using plenty of warm fresh water to remove any salt with techniques as detailed in the NEMA Publication.
With Total Extended Emmersion however, in sea or brine water, the dissolved salts present a great problem. The water and dissovled salts are drawn into spaces between the conductor and insulation via capillary action and later salts solidify after drying. It is impossible to completely remove such salt deposits no matter how extensive the removal efforts.
Therefore equipment such as motors, exposed transformers windings, and the likes must be overhauled and rewound at nearly the cost of new equipment or scraped and new equipemnt purchased. Cables must be totally scraped. Bus bars and other non insulated items can be clean with large amounts of warwm fresh water and then can be reused without problem. Switchgear, breakers, and the likes must be completely cleaned and overhauled with new and refurbished components under supervision of the equipment vendor or new equipment purchased.
Which ever route you take, restore or purchase new, it is strongly recommended that the safety and reliability of the electrical systems be of the higest concern with due consideration to all of the obvious economics issues.