Sailors are always looking for a good reason for a drink or six. This old practice over the years has come down to buying drinks for one another over a promotion. However that was not the original meaning.

Rank insignia at one time was actually made of gold thread. When exposed to salt air it would tarnish. When an officer would put on a new rank the new bands of gold were brighter than the old one. This would show off to everyone that the officer had just attained the new rank. This could lead to troubles in one for or another. So to prevent this new officer wet down his new rank.

He would soak his uniform in a bucket of salt water to tarnish the new rank and make it appear old. Also at the same time senior officers would try to catch the new higher ranked officer and splash him with buckets of sea water.

Over time as gold was used less and less the practice changed into a reason for a drink or two or six.