A little first aid kit in a watertight case and a watertight case for the cell phone would be on my list. Some matches in a sealed bag.
I am allergic to bee stings and the epi pen comes with me whenever I am far from the glove compartment.
A length of rope wouldn't hurt either in case you need to tie to a bouy to pull a hook out of your ear or tame a 40# cow. A knife in case the cow is towing you too fast into a freighter.
Other than that water, but that's a given.
sounds like a nice rig - ill have to check yours out this season
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