As memory serves, I believe this scene was near the Act II - Act III break. Moana is returning from the underworld being led by two giant mantas to the ocean's surface. (Apparently in animated movies no one gets the bends!)
The purpose of this sequence was twofold:
1.) To reunite Moana and her dad. Dad's love is demonstrated by his braving the open ocean (a tribal taboo), to search for his lost daughter.
2.) To have him present for the Act III climax to witness Moana's heroism. Moana thereby earning her fathers respect and admiration.
*The Kakamora beat served a minor plot point to show that they, along with the pig and the chicken, survived the wrath of the volcano goddess.
When this scene was first issued to me, one of the directors emphasized the importance of atmosphere to show the building threat of the Volcano goddess. Black waters, dark skies, driving rain, lightning, and choppy seas. Haha. No sweat!
My thought was that everything would be quiet and peaceful as she made her way to the surface, with a sudden change of sound as we cut topside to driving rain and rough seas, Moana gasping for air.
*Rain effects were easily simulated by overlaying filtered images of rain found on web.