OK, here’s an item that I was going to submit, until I came across the Plate armor of the deep… Note that this is not a submitted item, so we can feel free to discuss this, and pick it apart creatively and mechanically.
Sailor’s Armor Aura moderate transmutation; CL 11th Slot armor; Price 35,200 gp; Weight 40 lbs. DESCRIPTION
This +1 chainmail is slightly rusted and smells salty
When Sailor’s Armor is worn it acts as a normal suit of +1 chainmail. However, once per day, when submerged in saltwater, it transforms into +1 leather armor, with all the statistics of +1 leather armor. When transformed, it also calms the water in a 10’ radius around the wearer, reducing the swim DC by 5 but not lower than a DC of 10 in its area of effect.
The armor returns to +1 chainmail 1d4+1 rounds after leaving salt water. CONSTRUCTION Requirements Craft Magic Arms and Armor, instant armor, control water; Cost 18,060 gp