Workers on the delay-hit Woolwich ferry are looking to strike for 10 days due to a dispute over safety with Briggs Marine who run the service under license from TfL.
A total of 31 staff are unhappy are looking to strike on May 17, 20, 24, 28, and 31 and June 3, 7, 10, 14 and 17.
The ferry was formerly was under Greenwich Council control. It then moved to Serco before Briggs took over.
Introduction of new ferries has been beset by delays. One is named after a staff member Ben Woollacott who died on duty.
Staff are complaining of problems with diesel fire pumps not working on both vessels alongside changing shift patterns.