There are 7 Size Tiers and 20 sharks in Hungry Shark World
The Blacktip Reef Shark is the sole member of this group. It is also the weakest shark in the game.
The three sharks in this Tier are Megalodon , Big Momma (Dunkleosteus), Atomic Shark and the Killer Whale(!!). They can break any barrier and can eat Pink Jellyfish. The Atomic Shark can eat Red Jellyfish.
The Atomic Shark unlike the other tier "!!" sharks so far is the only shark that can be only bought after the shark before the Big Momma (Dunkleosteus) is at its maximum level (level 30) just like in Hungry Shark Evolution. It is the only shark that does not rely on healing via. eating due to the fact it can be healed by toxic waste barrels. It also will gain a short gold-rush-like effect when over barrels, however this will render the barrel unsuable again. It can also eat everything except for mines.