Depending on what you want for design, if you are around salt you want something in LC200N or H1. Spyderco does both folders and fixed blades in these steels, look for the Salt line. I think there are some other makers, but spyderco is what jumps to mind. 5Cr15 will be pretty rust resistant, but with salt water you easily get galvanic corrosion as you know, and LC200N and H1 are far more resistant to that.
This of course presumes you want something that you don't need to baby, wash, dry, oil, tend every minute. Some other folks will chime in if I've missed a steel that is also good in the salt.
What sort of uses/design are you looking for? Also, how much are you willing to spend, that will help others throw in some good advice.