Upvote:3
There are no international ferries leaving from Amsterdam, but there are ferries going from IJmuiden or Hoek van Holland.
IJmuiden is 27 km from Amsterdam and has ferry connections to Newcastle.
Hoek van Holland is 85 km from Amsterdam and has ferry connections to Harwich. You can buy a combined rail+ferry ticket that will take you from Amsterdam to London.
Both IJmuiden and Hoek van Holland are well-connected by public transportation.