A friend of mine was flying into PHL when he heard this on the frequency. As an avid LiveATC.net listener, he pulled it from the archives and sent it to me.
The local controller cleared an aircraft to land and instructed the pilot to maintain visual separation with a ship under the final. My friend tells me there is no VASI to the runway and it can be tricky landing, especially with ships in the way. Here's what the runway looks like:
Anyway, I thought it was pretty funny...enjoy.