Boat Race on a River

At the Futility Closet, a puzzle blog, we read: "Buoy Howdy From Russian puzzle maven Boris Kordemsky: Two diesel ships leave a pier at the same time. One travels upstream, the other downstream, each with the same motive power. As they depart, one drops a lifebuoy into the water. An hour later, both ships reverse course. Which will reach the buoy first?" http://www.futilitycloset.com/2013/07/25/buoy-howdy/ I wanted to make a model. What happens if the buoy can be dropped in different times? What if the boats travel different speeds? Does the speed of the river's current matter? What can you find out?