In chapter 7 of A Separate Peace, what does Gene mean when he refers to the appropriateness of being thrown into the Nagaumsett River on the first...

There are two rivers in A Separate
Peace, the Naguamsett and the Devon.  In Chapter 6, the Naguamsett River is
described, in part, as "...ugly, saline, fringed with marsh, mud and seaweed.  A few
miles away it was joined to the ocean, so that its movements were governed by
unimaginable factors like the Gulf Stream, the Polar Ice Cap, and the moon."  The Devon
River is quite the opposite.  "The Devon's course was determined by some familiar hills
a little inland; it rose among highland farms and forests which we knew, passed at the
end of its course through the school grounds..."  Furthermore, it is the river where the
boys had "so much fun, all the summer."

At the beginning of
Chapter 7, Gene states that "the Devon was like taking a refreshing shower itself, you
never had to clean up after it, but the Naguamsett was something else entirely."  He
further says, "...it seemed appropriate that my baptism there had taken place on the
first day of this winter session, and that I had been thrown into it, in the middle of
the fight."  Gene is referring to the fight he has with Quackenbush when Gene starts
working as the assistant senior crew manager.

Gene believes
it is appropriate that he is thrown into the ugly Nagaumsett River because it is the
river whose movements are decided by "unimaginable factors."  This is similar to what
has happened to Finny.  It is unimaginable to Gene that Finny is injured and not at the
winter session.  Gene also feels guilt for jouncing the limb and therefore, feels dirty,
much like the river.  Both Gene and Finny's plans for their lives have been affected by
Finny's injury and the war, both "unimaginable" events.