re: To hold the water or to drain.

You really should drain it. Even cold water conducts cold away from ice much more efficiently than cold air.

I travel to our hunting lease for a week at a time. Tried a bunch of things over the years but by far the best thing is to use large blocks of ice and big cubes.

Frozen 1 gallon jugs of ice worked pretty well until I discovered silicone ice block molds. Volume of water is about 1.8 gallons or so each. I freeze 2 blocks for each cooler. I put them in and then fill with cubed ice... never crushed ice. I can be gone for a week and come back and still have a reasonable amount of ice left. Blocks are 3/4 melted after 6 days in hot to warm temps.

Does not matter if Yeti, Coleman, Igloo. Results are about the same. I have found bigger ice is the key.

One of the guys on the ranch swears by dry ice in his spare cooler. He fills his coolers and then puts 3-4 pounds of dry ice on top and shuts the cooler and does not open it until his primary cooler needs more ice in a few days. He seems to do okay on ice. You just can't put food in a cooler with ice and dry ice unless you don't care that whatever food you put in that cooler is frozen like a rock for 2 days until dry ice is gone.