Travelzoo offers a CitySights New York Hop-On Hop-Off Sightseeing Ferry Tour for $18. That's tied with our mention from two weeks ago as the lowest price we could find by $17. This 90-minute ferry tour offers hop-on/hop-off access at several New York locations, such as Times Square, Brooklyn Bridge Park, and World Financial Center. Book this travel deal by March 31 for cruises through the same date.
Of note, you may also buy a Child's Ticket for $12. That's the best deal we could find by $9.