I suspect that there's niches where battery electric boats and maybe planes do make sense.

My state's ferry system is investing in electrifying, because they project it reduce operating costs. The 'easy' part is moving towards hybrid systems that can move with diesel or battery; this is projected to save fuel even without shore charging. The hard part will be making shore charging work. Our grid is mostly hydro, so switching from diesel to electric should be better for emissions and the operating budget.

If the routes were longer, shore charging wouldn't be very relevant, but they're short enough that many routes could work without diesel most of the time.