Especially near water, you will very quickly have a build up of muck on your lens. You may not even notice it happening but when you get home and upload your photos you'll be faced with a massive cleanup job (of your images and lens) or worse.
The fine mist around coastal shoots or near waterfalls needs to be cleaned off regularly, sometimes between each and every shot. You will certainly notice the difference.
Just the simple act of wiping down your lens could mean the difference between a great shot and a binned shot.