Many people would leave their phones to charge in the bathing houses or they'll just charge them in their cars. You can always try to buy a portable charger at a store if you want to in the end. Totally understandable if you feel hesitant in leaving your phone at the bathhouse, this is my 5th year coming to this campground and I haven't had any issues yet
There is also a small lounge at the Marina Store, didn't go inside but I'm assuming there are outlets there. You can always call the store to find out.
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