The Marino cable
EEL Cordset, 30A 125V, 12', YellowPart # CS30-12
is rated at 60C so already you have a problem with your temperature spec. Presuming your intention isn't to prohibit what everyone uses.
There surely must be a relevant UL test spec for cables in damp locations. I guess I would talk to Marino or Smart plug and try to figure out how to specify the cable. What problem do you have now that you are trying to solve? Are people using indoor type extension cords?
The second item would be how is the cable deployed, as noted you want it not to present a hazard ,tripping, dock cart or electrocution.