I assume you are joining for just the standard 4yrs? Consider the 1st year to be a wash, you'll have Boot Camp, BE/E and your "A School" to worry about. I can't remember if EMs go to "C School". Depending on your orders, you may or may not get assigned to a ship.
Depending on the class of ship, you may or may not have the time for independant study (depends on staffing). As soon as you are out of Boot Camp get to your Educational Officer, get your hands on everything they offer you. You won't be on the water 24/7, the hard part is when not deployed to keep your focus when in port.
If you manage shore duty first, you'll have a greater possibility of finishing that degree.
"Art without engineering is dreaming; Engineering without art is calculating."
Have you read faq731-376 to make the best use of Eng-Tips Forums?