Bite. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 41 (5d12 + 9) piercing damage. If the target is a creature, it is grappled (escape DC 23). Until this grapple ends, the target is restrained, and the megalodon can't bite another target.

Breach (Recharge 5–6). The megalodon can leap out of the water to attack creatures on the water's surface or hovering above it.  The megalodon uses the Dash action to move vertically upwards towards a target.  The target may be any creature or object floating on or flying up to 40 feet above the water's surface.  If the megalodon moves at least 20 feet before reaching the surface, it may launch itself from the water up to half the distance it traveled during its Dash action into the air.  The megalodon can then make a bite attack against the target.  If the bite attack misses, the megalodon uses its ram attack against the same target, with the movement taken during this action counting as the movement requirement for that attack.

Ram. If the megalodon moves at least 30 feet as part of its movement, it can then use this action to move into a 15-foot cube, centered on the tip of the megalodon's snout, that contains one or more other creatures. Each creature in the area must succeed on a DC 23 Strength or Dexterity saving throw (target's choice) or take 30 (6d6 + 9) bludgeoning damage, and be stunned for 1 minute. On a successful save, the creature takes only half the damage, isn't stunned, and is pushed out of the megalodon's space into an unoccupied space of the creature's choice. If no unoccupied space is within range, the creature instead falls prone in the megalodon's space.

A creature stunned by this action can repeat this saving throw at the end of each of its turns, ending the effect on itself on a success.

Swallow. The megalodon makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the megalodon, and it takes 28 (8d6) acid damage at the start of each of the megalodon's turns.

If the megalodon takes 30 damage or more on a single turn from a creature inside it, the megalodon must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures,which fall prone in a space within 10 feet of the megalodon. If the megalodon dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Tail. The megalodon whips its tail in a 30-foot cone originating in the space immediately behind its dorsal fin. Any creature in the area must make a DC 23 Constitution saving throw, taking 18 (2d8 + 9) thunder damage and being stunned for 1 minute on a failed save, or half as much damage without being stunned on a successful one. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

The megalodon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Bump. The megalodon moves 30 feet and makes one ram attack at the end of the movement.

Dart. The megalodon moves up to its full swim speed.

Thrash. The megalodon makes one tail attack.

Chomp (Costs 2 Actions). The megalodon makes one bite attack or uses its Swallow.

Death from Below (Costs 3 Actions). The megalodon makes a breach attack.  The megalodon must be at least 20 feet below its target before using this action.