A passive aggressive insult to remind navy personnel that they are in fact in the navy. There are no good days in the navy, so it basically means have a shitty day.
It means that your acceptable weird. Some people are weird, but it's like dorky weird. People who are weird in a good way are not dorky but they have their own style, they're not scared to be themselves, and they stand out as different in a good way. Overall it's a compliment for the most part.
"I just do me and idc what othersthink!"
"You're weird (but in a good way)"