n large animal aquatic 

Perception +10; aquatic echolocation 120 feet, low-light vision

Skills Athletics +10

Str +5 Dex +3 Con +4 Int -4 Wis +3 Cha +0

Aquatic Echolocation A narwhal can use its hearing as a precise sense at the listed range, but only underwater.

Deep Breath A narwhal can hold its breath for 30 minutes.

AC  18; Fort +9, Ref +10, Will +8

HP 50

Speed swim 60 feet

Melee [>] tusk +12 (reach 10 feet), Damage 1d10+5 piercing

Melee [>] jaws +12, Damage 1d8+5 piercing

Impaling Charge [>>] The narwhal Swims twice and makes a tusk Strike. If it moved at least 20 feet from its starting position, the narwhal deals an extra 1d10 damage on this Strike. A target damaged by Impaling Charge is grabbed until the start of the narwhal's next turn unless it Escapes before then (DC 20). The narwhal can't Grapple to extend the duration of this grab.

Bestiary 3, page 184.