Hits water and bogs down alot. Sparkplug issue?

Hey guys my 03 400 Sportsman runs great when I don’t hit huge water holes but as soon as I hit a big hole, like to the top of the tires, it bogs down hard and seems like its misfiring or something. It never used to do this but started last year and wanted to fix it this year. The wheeler only has 1900 miles or less if I remember right. Think a new spark plug with dialetic grease on it would help? Ive never changed it and I got it with 400 miles. Any other ideas? Thanks!