someone should design a floating head that you can rig plastics on... different shapes... maybe a cupped popping head... I know I've seen something like that for freshwater...
or maybe you could inject air in a sluggo, like they do for freshwater plastic (and live) worms...
after a little googling, I cant find any floating soft jerkbaits..... just the 11" floating worms, but I don't think that's what you're looking for...
3rd edit: develop your own, and make it out of cyberflexxx... it floats like a cork and stretches like a rubber band... if you wrap a rubber worm made of cyberflexxx around a 15 lb. weight you can pick it up...
http://www.worldrecordbass.com/article.asp?ID=61