The outlet located closest to the AC panel should be first in the series of chain outlets and should be a GFCI. The cable used should be 16-AWG or 14-AWG marine
grade cable depending on intended loads.
grade cabling specification are pretty simple to understand and you can buy marine grade cabling at Home Depot and other such places if you understand what "Marine Grade" actually means: Stranded copper wire with a wire strand cross-section suitable or higher than the planned loading/amperage of the circuit to be installed. Tinned leads (with a bit of practice one can tin the leads themselves with a soldering iron and good quality solder), and a cable insulation
heat coefficient of 105-degrees C or higher. (Note: Marine Grade speaker wire for your sound system will probably have to purchased from a company that specializes in marine cabling...Ancor, for example.)
I try to purchase
outlets that have removable screws on them instead of the "slip the lead in the slot and tighten the screw on top" kind. Removable screws allow the use of installing ring-type crimped terminal lugs. I do not recommend the use of spade terminal lugs because if the screw becomes loose due to vibration the spade lug may fall off the terminal. For a ring lug to fall off, the retaining screw has to have fully unscrewed and fallen out. Chances are you will know that this is happening well beforehand due to intermittent power outages at an outlet.
Now, and again, this is my personal preference when connecting electrical
leads: I seal the end of the cable where the individual leads are exposed with 3M liquid insulation
and once dry, cover in appropriately sized heat shrink to prevent moisture/humidity from intruding into the cable sheathing. I do the same to any crimp connections.
The allowable exposed leads coming out of a cable is 30-inches. Try to include chafe protection for exposed leads where possible.
And last, properly secure the cable run. Nothing more annoying than hearing a cable flop around underneath your bunk because it is not being held in place properly.
My 2-cents worth. There are other ways to do this easy installation
, I know, but this is my preferred method.