Do I need to do anything special when installing lead-acid batteries on or near water?
Installing batteries in marine applications (especially salt water) requires special attention.
The cables used should be marine-approved and should be tinned copper. If you use any other cable type, be prepared to spray and coat the cable and connections with silicone or grease, such as Vaseline. Use silicone-lined heat shrink tubing to cover terminal connections to protect against corrosion. The main concern is protecting the marine atmosphere from exposed terminals or connections.
CAUTION/DANGER: Do not allow battery electrolytes to mix with salt water. Even small quantities of this combination will produce Chlorine gas that can harm you and cause death.