Just like Disney, Sea world is crowded Christmas week. the difference is there are no lines to get into the stadiums to see the shows, but the stadiums will fill up fast so you want to get to the shows early.
The 3 rides will have long lines, but if you wait till evening a lot of people will have gone home so the lines lighten up some. Single riders get on quicker, so if you don't mind that you get to ride faster and more times.