Travelzoo offers a CitySights NY Hop-on Hop-off Sightseeing Ferry Tour for $18. That's tied with our mention from three weeks ago and the lowest total 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, 2017 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.