Under the command of Capt. Adam Aycock, the USS Shiloh became known in the Pacific as the "USS Bread and Water." It seems Aycock's favorite non-judicial punishment for his junior enlisted was an old but legal punishment that confines the sailor to the brig with nothing but the world's simplest combo meal.
Works for ducks. Why not you?
According to the Department of the Navy Corrections Manual, "Confinement on Bread and Water (B&W)... may be imposed as punishment upon personnel in pay grade E-3 or below, attached to or embarked in a vessel."
Article 15 of the Uniform Code of Military Justice outlines the punishment further:
• It may not be implemented for more than three consecutive days.
• Rations furnished a person undergoing such confinement shall consist solely of bread and water. The rations will be served three times daily at the normal time of meals, and the amount of bread and water shall not be restricted.
• The medical officer must pre-certify in writing that a deterioration of the prisoner's health is not anticipated as a result of such action.
• Prisoners serving this punishment will be confined in a cell and will be bound by the procedures set forth for disciplinary segregation cells. They will not be removed for work or physical exercise.
While the Bread and Water punishment sucks and does seem rather archaic, it's hardly the worst punishment that can be handed to a sailor at Captain's Mast — especially for an E-3 or below.
"La Croix and toast" is probably not happening.
Captains can send sailors to the brig for 30 days, forfeit their pay, take stripes, assign extra duties and restrictions, or any combination of these. As retired Navy Captain Kevin Eyer pointed out in a Naval Institute article on Bread and Water, the "arcane" punishment of Bread and Water only affects the sailor. This is especially important if the sailor is married because the other potential Article 15 punishments would affect the whole family.
As of December 2017, the elimination of the Bread and Water punishment was up for review by President Trump.