Try humming any of the following:
The Cassions Go Rolling Along
Anchors Aweigh
Off We Go
The Marine's Hymn
Semper Paratus.
Hail to the Chief (words provided upon request)
Even if it doesn't work people will know that you support the President and our troops.
I was recently surprised when I accidentally came across the words to "Hail to the Chief" myself.
I thought, "Holy cow: there are words to this thing?"