I have been using 50-foot 10 GAUGE (10-3) with a RV30A-15 long "DOGBONE" type ADAPTER from day one (2008). I found the two HD YELLOW 10-GAUGE CONTRACTOR GRADE cords from a yard sale at a great price compared to what they cost at the store..
I would steer away from using these small black roun RV30A-15A ADAPTERS. All that I ever used with the RV 30AMP Shore power Cables always got hot on me after being used for a short time. You donn't want to burn up your expensive extension cords or shore power cable ends...
I also picked up a couple of 25-foot 10-gauge RV 30AMP extension cords from the local Dealer when I got my 5th wheel from them. They have a hugh lot with many trailers sitting in it all hooked up to Electric using these... These have come in handy numerous times when my shore power cable is just three feet short when hooking up at the camp ground pedestal.
Another trick I do here is always have a RV 120VAC METER plugged into a 120VAC receptacle inside my trailer in a good spot so I can glance at it before turning on something high wattage like the air conditioner or microwave. It the 120V is not within the SAFE GREEN SCALE I will not turn the high wattage items ON.
The heavier gauge may pay off big at your fish camp with many others there all hooked up at the same time...
All of my connections are cool to touch laying out on the ground when being used. These cables all work good with my 2KW Generator as 120VAC source when being used as well...
Roy Ken