Using shore power on boat w/o AC power system

[dalepo]

I have a 22' boat with no AC inlet or power system, just a single 12v battery, used to power the radio and lights, that I keep charged with a small solar panel.

There are times when I work on the boat at the marina or sleep onboard when I'd like to use shore power to run small electric tools, a fan, phone charger, etc. I have an inverter, but I find that it runs the battery down faster than my solar panel can charge it up again.

The question is this: would it be safe to use an adapter to connect the 30 amp shore power outlet to a standard heavy-duty 15 amp extension cord and then run that into the boat through the hatch to power low-amp AC devices whle I'm working / sleeping onboard?