Tie up anything loose, keep decks clear.
Muster into safe zone of the boat.
Switch off systems that will attract the lightning.
Check for any leaks and if found, prevent flooding.
This lightning shower caused power cuts and the risk of fire but TandEadapt was moored at a pontoon. Properly tied down with springs and mooring lines. If on water, I would find the quickest way out of what's called, 'The danger zone.' With hurricanes anyway. But the same principle applies if in this distress. Move to where the cyclonic winds are less and leave the area of the storm.