This year I made gel ice packs by buying a package of diapers, soaking them then vacuum packing them. I have a vacuum chamber packer so I can seal the bags while they're still wet. They worked great. $8.00 for 25 diapers each about 16" long. Reusable too.
If you use a Foodsaver freeze them first them vacuum pack. I kept them all in a cooler with dry ice which kept them frozen hard for 2 days til I used them. I did replace the dry ice daily though.
They worked great. Layer of fish, layer of diaper ice, layer of fish......
Keeps the moisture to a minimum in the coolers.
Anyone ever bought ice from the commercial guys near the public boat launch? I've thought about that but never done it.