Just my opinion, but I think you'd be better off with the meat tightly wrapped in foil and just blankets/towels in the cooler. The water might cool off sooner than the meat would wrapped in its insulation. You want the meat to stay above 140 degrees. Tap water is usually around 125, so you'll actually be cooling the meat down. You'd have to use very hot water and then hope that it didn't cool down to below 140. Without water, you have thermal mass working for you rather than against you.
Again, you won't have any problem keeping the meat hot for at least 4-6 hours just wrapped in foil and towels.
Jeff