Yeah; 5-Ft clearance is not enough. The VHF might take a few feet if not accounted for in addition to high tide. If you are within a few feet the electricity might just arc across if it is high voltage. We sailed beneath a train trestle here in No Ca that had a minimum clearance to the mast of about 10 feet. It was VERY nervous until we passed through! Read your charts carefully; the mistake of hitting a power line is and should be preventable.
If hitting one is imminent you should not touch anything metal that could conduct to the source of power (like the rigging, lifelines, helm) and hopefully the decks are dry. If you are not instantly killed you are probably best to stay aboard until the power gets shut off; if you go in the water the electricity will most likely paralyze you and stop your heart (it only takes something like 50 milliamps to do that). A boat can burn for a long while before sinking; I would wait to be sure that the electricity is shut down before abandoning.