I agree that the answers to these questions depend on definitions

I think he meant that those questions depend ONLY on definitions.

As in, there's a lot of interesting real world knowledge that goes in getting a submarine to propel itself, but that now we know that, have, people asking "can a submarine swim" is only interesting in deciding "should the English word 'swim' apply to the motion of a submarine, which is somewhat like the motion of swimming, but not entirely". That example sounds stupid, but people waste a lot of time on the similar case of "think" instead of "swim".