Yeah, I think if people go all-in on electric boats, they are going to want to install a fast charger. If and when sales take off, I suspect most marinas will have charging stations just like they have shore power, fresh water, and fuel for sale today.
EVs--on land or water--are always going to make less sense for high mileage/long trip users. In my local context, it would a tough sell for someone pulling lobster pots 4 hours a day 30 miles from the mooring, six days a week. But might make a lot of sense for someone planning a start and stop trip fishing for a few hours once or twice a week.
Costs need to come way down and we need to see these things work in practice before most of us will consider this.
My wife and I considered an EV for our last car purchase, but for our driving pattern, the amount we'd save fuel over the ~50 mpg we get from a hybrid would not have made up for the higher monthly payments. My guess is that will be different when we buy our next car in about 8 years.
Not so much when we replace my truck--fewer EV options, all very expensive, and range for multi-day trips off pavement into the woods is a real concern.