When going out on the town and picking up conquests.

One who only fishes in the Harbor.

Respectable fishermen, fish the open sea and bring their catch to the Harbor for sorting and selecting.

Less than honorable fisherman await the deep sea fishermen's return and and attempt to pilfer their catch.

Occasionally fishing with in the harbor is acceptable as long as that person is know to go deep sea fishing and stocks the harbor. One who fails to stock the harbor, though fishes within it, almost never fishes in the deep sea may find themselves becoming a Harbor Shark
Manny Moe and Jack are staying in Vegas for the weekend, Manny and Moe go out hit the town for hours and brings back 5 girls to the hotel bar. all the while Jack has been sitting at the hotel bar, and seeing that his friends are back with girls Jack instantly swoops in and goes for the hottest girl, hence being a Harbor Shark
by Haywood Jablowmie pdx July 18, 2010
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