Submarine is referred to as boat, not ship.
That was the funniest thing he said, because anybody who actually knew what they were talking about would have said “boats”. Because submarines are not called “ships”, they are called “boats”.
This is a Naval tradition, even though some modern subs are big enough to be classified as ships. But Obama probably doesn’t know that there are size classifications.
He probably does know that the Navy uses the term “ship” in their budget document, which is probably as close as Obama comes to understanding the military.
On the other hand, when I first heard he said “we have ships that go underwater”, my thought was “yes, that is what happens when you cut too many ships out of the navy, and we can’t defend them, and they get torpedoed and sink”