https://www.fleetzero.com/ https://www.fleetzero.com/ is proposing to build electric ships and, yes, swap batteries. They build the batteries in the form factor

https://www.fleetzero.com/ https://www.fleetzero.com/ is proposing to build electric ships and, yes, swap batteries. They build the batteries in the form factor of a shipping container, so existing port infrastructure can be used to perform the swap.