The Sol is not a fully waterproof reel only the drag is waterproof. So you wouldnt dunk it in saltwater. But the difference is the bearings. Theyve got some sort of rust protection on it but not all of them. Saying that Ive got the 2500Sol since it first came out and still going strong No rust last time I opened and serviced it so I would say they are good. Shimanos are good as well as I think they got the fluid drive which u can put oil at the maintainance port w/o leaking. Or If u want a full waterproof reel you have to get a stella or a saltiga.
Im not a pro, dont know if theres any other reels in the shimano or daiwa range w/c is fully waterproof.
Im sure some Raiders will be able to help u with this topic.
Goodluck,
JON