Anyway
There are 5,585 km between London and New York, that is 3,470 Miles. It's probably a bit more than that by boat because you have to go around Kent.
Very large and modern Catamarans can travel at speeds of around 80 killometers per hour or 50 miles per hour.
Is it feasible?
Well, no. You would be at sea for more than 2 days and then more than 2 days coming back again. I think people wouldn't want to spend 5 days at sea to go on a trip. Plus the cost of paying the crew for more than 2 days would add up so it wouldn't be significantly cheaper than flying there. Unless you made them go faster so they did the trip overnight or inside one day. The large ones that would take passengers don't go anywhere near the speed needed to cross the Atlantic in one day.
You would need to travel nearly 150miles or per hour , 230 killometers per hour constantly just to reach America , but you can't because you would be crossing busy shipping lanes. You would need to slow down and be prepared to stop at certain points. Perhaps if they went to Bristol instead of London they would fare better.
That's my verdict. With today's technology it isn't feasible to travel to from Europe to America by boat. You won't save much money and there would be many costs that emerge to the company providing the service.
