You need to completely submerge it in fresh water to help get rid of the salt that is imbedded in it from being in the ocean for many years or it will keep rusting and it's condition will worsen rapidly now that it's exposed to air, you will have to changed the water every week or two as the salt starts leaving the relic and leaching into the fresh water, eventually the relic will reach a stable point and you can dry it out and seal it, sealing it with the salt in it will not stop it from continuing to decay!!!
If you live in an area that gets lot of rain, a rain barrel at the down spout of a gutter is the perfect place to place the relic so you don't have to worry about having to change the water for a new batch of fresh water, the water will get a refreshing every time it rains, if no rainfall for a period of time, stick the garden hose in the barrel to refresh/replace the water.