Restrict Polyphemus to the Shoals, and make sharks not appear in the

Swamp (randomly on water levels with a lot of water, is okay).

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8032 c06c8d41-db1a-0410-9941-cceddc491573

Created by  j-p-e-g  on December 30, 2008
243PID7FPL3QF5DFJAY3KDUFEV3CUBZDFSAAFI4OCY5GLBIY5QYAC
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