The 31 meter long, 366 dwt tug CMM Coatzacoalcos sank in the Coatzacoalcos Quaschnick River near Coatzacoalcos, Mexico.  The tug was working on an underwater construction site when the tug suddenly sank.  Three of the crew on board were rescued, but the master and chief engineer perished.  Reports state the river conditions were difficult due to recent rainfall the previous days.  Authorities have launched an investigation into the incident.