These sharks are found in East Freeport, too. Right by where Giz Dinree (at night) and Bait Masterson (at day) spawns. They hit me for about 16 damage. They regain health really fast too.
There is a paladin quest in Freeport, which has a reward of a sharkskin shield. It's a pretty crappy shield(ac2 I think), but if you want it, kill these sharks for the sharkskin component of the quest.
Also a quick and dirty way to raise elf faction. If, like me, you're dumb enough to kill an elven slave in CB (my DE roomie wanted to see the faction hits), you can use the shark meat to make the merchants in Felewithe like you again (good when you're a High Elf Wiz).
Level 4-6? That's one little prick of a shark. I'm used to conning sharks at level twenty and getting: A 'soandso' shark scowls at you, ready to attack -- what would you like your tombstone to say?