Originally Answered: Is this writing OK? A boy is caught in an undersea world?
You've got some really good parts, and some parts you can work on. Overall, yes, I'd say it's pretty good. It's really hard to judge one simple scene, completely out of context, but I'd say you definitely have potential.
A few things you want to be careful about: your character angsting too much. It gets boring. I don't know how often he does it, though, so I can't really comment.
Show, not tell. You have to tell certain information, and that's fine, but when you started saying things like "Oliver's past cruelty," I'm not inclined to believe you. This would be a perfect time in which you could include the dream, show the relationship between Andrew and Oliver, and really show how Oliver was being cruel. I'm more inclined to believe when you demonstrate a character trait, like Oliver's cruelness, through action, than merely telling me he's cruel.
Also, watch your to be verbs. Be, am, is, are, was, were, been, have, has, had, much, may, might, can, could, and many more. Writing without to be verbs imparts a far stronger and more interesting message than writing speckled with them. Of course, fiction is different, but still, get rid of as many as possible. Keep things in the active, not passive or progressive, whenever possible.
Also, I haven't really seen any other characters except for this Andrew, but I get the feeling he's the protagonist, so make sure he's not a plaster saint. Also, make sure other characters have their own lives and motivations besides making him sad/comforting him/helping him/hindering him. The world should not revolve around the protagonist.
There's really too little for me to say much of anything. I think this sounds pretty good, but without the rest of the chapter, or even the rest of the manuscript, I can't really say. I like your phrasing, especially "pulse of the current." Very nice, subtle personification going there.
I say good job, and you show potential.