Jaroslav Hornof did what he was supposed to do: he reported to his employer that he had found evidence that a former chief engineer on his German-controlled bulker had illegally discharged bilge water into international waters.

But not long after, it was Hornof who faced a warrant for his arrest.

The Czech third engineer is among mariners who have been held as witnesses in hotels across US port cities — some of them hungry for a whistle-blower award, some yearning to return home — as the government continues its pursuit of shipping companies that it alleges dump pollutants into international waters.