I've had a similar experience- I've had "high-carbon" knives rust from just salt air, with no exposure to liquid at all, and I had a Spyderco Endura that I used to wear clipped to the back of my waistband while jogging (sweat) rust on me... and, of course, innumerable cheap "tackle box" knives have rusted over the years with almost no provocation.
Diving and sailing are realms where a knife is absolutely essential (to my mind, the ban on automatic knives, aside from being just ridiculous, was especially unfair to sailors, who's lives can easily depend on a knife and who rarely have two hands free) and both realms routinely involve highly corrosive environments.
It may be true that everything is a compromise at present, but the compromises are getting better- Beta Titaniums are not bad at taking and holding an edge, are light and very corrosion resistant, some Stellite alloys are very good (but very expensive)... and Liquidmetal seems to have huge potential in the field, being light, strong, corrosion resistant, and having the potential for extremely inexpensive fabrication- it's melting temperature is low enough that knives with edges ready-to-use can be injection molded. Things may be changing in the next few years.
Maybe it's just me, but, especially as I get older, I tend to think there's some correlation between "low maintenance" and "high quality". I hate having to constantly fiddle with and baby equipment, I hate to pay a lot for something and then see that it comes with elaborate "care instructions", and, especially with survival gear, it seems to me that part of it's job is to take care of itself enough to be ready when and if it's needed.
Needless to say, there's apt to be precious little time and opportunity to baby equipment *during* a survival situation. Someone fighting for life on a boat or island is unlikely to be able to take time to rinse, dry and oil a knife to keep it from rusting.
It may be that the knife that's in routine daily use on the water will not tend to rust, as it's easy to keep an eye on, at least... but how many people on this forum are the sort of person that would go to sea with only one knife? <img src="images/graemlins/wink.gif" alt="" />