Blood Frenzy. The shark has advantage on melee attack rolls against any creature that doesn't have all its hit points.

Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5+the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Levitate. The undead shark is able to fly and has a flight speed of 35ft.

Deconstruct. The undead shark is able deconstruct itself into a pile of decaying flesh and bones. While its in this state it has a +10 to stealth checks.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 22 (3d10 + 6) piercing damage.

Deadly Charge. If the undead shark moves at least 15 ft. as part of its movement, it can then use this action to charge towards to a space 50ft. in front of it that contains one or more other creatures. Each of those creatures must succeed on a DC 14 Strength or Dexterity saving throw (target's choice) or be knocked prone and take 14 (3d6 + 4) bludgeoning damage plus 14 (3d6 + 4) piercing damage. On a successful save, the creature takes only half the damage, isn't knocked prone, and is pushed 5 ft. out of the sharks space into an unoccupied space of the creature's choice. If no unoccupied space is within range, the creature instead falls prone in the undead sharks space.