These are modern pirates performing maintenance on their sailboat.
Dit zijn moderne piraten die onderhoud uitvoeren op hun zeilboot.
Pirates are fixing someone else's sailboat.
Piraten repareren andermans zeilboot.
Pirates are fixing their sailboat, or fixing someone else's sailboat. Not at the same time.
Piraten repareren hun zeilboot, of repareren de zeilboot van iemand anders.