The first two lines have nothing to do with the rest of the song. The sun shined through his window and he changed his ways in some unspecified way. The rest of the song is Donovan trying to pick up a girl. He says he was at a beach with her at sunset. He tells her that he will be fantastic in bed, as in "slowly blow your little mind". He refers to himself as a superhero (Superman or Green Lantern have nothing on him), and what he bases his greatness on is the fact that he will make like a turtle and dive for her pearls in the sea, which is a very sneaky way of saying he will go down on her. There's your song. Donovan telling a girl he will go down on her like Superman.