In "Musee des Beaux Arts" by W. H Auden, what do the people on the ship do after the see Icarus fall into the sea

They kept sailing.

The poem says that the people on the ship " Had somewhere to get to and sailed calmly on." This supports the fact that no one around really cared too much about Icarus falling into the sea; everyone else in the painting looked like they had more important things to do or worry about.