A majority of the experienced fishermen in the SE use a Polar Bear Cooler. This cooler is the number #1 Choice in our part of the country. While it comes in various sizes, the 24 pack seems to be the size of choice for most of the Hobie owners.
This soft-sided cooler is one of the very best you can get. It will keep ice all day long under the FL sun. They aren't cheap but well worth the money. You can't do any better than this soft-side cooler.
They also sell a cooler liner that is a heavy duty ziplock type bag. It is perfect to keep your fish in. Simply drop your fish into the bag, roll it up and stuff it in your cooler. I have used my liner for over a year with no punctures.
Polar Bear is also one of the major sponsors for the various kayak fishing tournaments in the SE.http://www.polarbearcoolers.com/