The sea-monster Simhika seized Hanuman's shadow, using magic to pull him down towards her.
Hanuman allowed Simhika to swallow him, but then he expanded inside her, bigger and bigger, slashing with his claws, until Simhika exploded into a thousand pieces, and the ocean's waters turned red with her blood.
Hanuman then rose up into the air and continued his journey to Lanka.
The gods had been watching, and they sang Hanuman's praises. "You will surely succeed in your quest, Hanuman!" the gods all shouted.
Inspired by: Sita: An Illustrated Retelling of the Ramayana by Devdutt Pattanaik
Notes: This story is on p. 193 of the book. In Valmiki's Ramayana, this is the Sundara Kanda (Book 5), sarga 1.