Blood and water

You are on a sinking ship. There is only one life buoy left. Your father is out in the choppy waters to your left. To your right your lover is signalling for help in the sea. Who do you throw the life buoy to?

That was the question thrown to us by our Mancunian English teacher at school.
"Personally, I'd save my girlfriend," said the teacher, "because I chose to be with her, but I didn't choose my father."
"But blood is thicker than water," said a girl in the back. " I would choose to save my dad."
I was wrestling with the question. Do I choose my dad? Do I choose my lover? Am I a lunatic for even having to hesitate in choosing my dad between the two?
"I'd save my dad, because I think my dad can't swim," I said.
"What if your lover couldn't swim either?" asked the teacher.
I scratched my head again.
"Well, hopefully, my lover would be younger and fitter than my dad?" I said. "I could throw the life buoy to my dad, then swim over and rescue my lover, how about that?"
"You'd both drown," said the teacher.

What would you do?