What cooler should I get for a boat to prevent sliding?

Get a Yeti Tundra or any heavy-duty roto-molded cooler with integrated tie-down loops and thick rubber feet. The weight and aggressive rubber feet keep it from sliding in normal chop, but you should still strap it down. For a cheaper option, try RTIC or Pelican. Don’t get a soft cooler or a cheap Coleman—they slide, tip, and insulate poorly.