Chris,
We were on the Explorer in April, and did not feel out of place at all with a tux. Two of the Three other men at our table also wore a tux to both of the formal nights. Also, a blazer on the non-formal nights would have been OK also. I did wear one on one of those nights and did not feel out of place.
We sailed out of Miami, and arrived at the pier around 11:30 and was on the ship around 12:15. The embarkation process went very smooth.
Have a great time. :cool: