Thank you, I hadn't though of several of those things. But it still begs the question. Which system is more costly:
1) High voltage DC charging that can fill a boat in less than an hour, enabling the need for fewer chargers, but requiring more costly electronics on each boat.
2) Enough places to moor overnight each with mains power so every electric boat has a place to moor and charge, mostly with existing electronics on each boat. Eventually, this would be needed for every boat.
We can't do the math without making some assumptions on size of battery, typical boaters daily needs, summer vs winter, etc.
I'm thinking that a middle of the road solution is needed between DC fast charging and 30A mains charging. I don't think it is practical to put 20,000-30,000 mains hookups on the canals/marinas.