All was ready; I launched my raft, and was loading it with my property, when my eye caught sight of a shoal of fish darting up through the passage, followed by a black, triangular fin, which I quickly recognised as that of a huge shark.  I saw the horrid monster overtake and gobble up some of the fugitives, and then quietly come back, as it appeared, to swim sentry at the entrance of the lagoon.  Perhaps he knew that the fish would make an attempt to get out again the same way.  Be that as it may, I felt no inclination to encounter the gentleman.