"Troubled Pleasure," - uses a oxymoron to show that he feels some guilt for stealing the boat, but it feels good all the same.
"Wentheavingthroughthewaterlikeaswan;" - simile and a oxymoron to show how the boat moved gracefully and elegantly.
"a huge peak, black and huge" - change in tone in The Prelude can be seen. It shows that nature isn't what it seemed - it is powerful and can be seen as a monster.
"By day, and were a trouble to my dreams." - his encounter has changed him.
Themes:
insignificance of man
fragility and morality
mankind small compared to nature - storm on the island