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The part about not being closer than 5 feet to the water is generally non-negotiable. It is, however, called a 'reach radius' and so you can put the panel under a shelf or inside of a cabinet if there is a door or ledge. The idea is that if you have to reach around something permanent and that distance is over five feet you are good.
I have a spa on a deck hooked up to 120v GFI outlet under the deck. The actual distance from the edge of the spa to the outlet is probably 3 feet but the spa is on top and the outlet underneath....so this is OK?