Four ragtag pirates in a lifeboat without power in the middle of the ocean surrounded by USN ships is not exactly a great negotiating position--for them. We hold all the cards re their safety. Give them an ultimatum--release the captain or you will die. Let's see how suicidal they really are. If they refuse, then we use SEALs to go after them at night using night vision equipment, stun grenades, and silencers.
Exactly, killing four exposed men in rapid fashion without killing the hostage is doable.