When the mysterious storm hits Seattle, the water forms a physical, rubbery, liquid-like forcefield along the perimeter of every home, preventing doors and windows from opening. The film jumps five years into the future. The Delgado family has adapted: they grow crops indoors, collect rainwater, and use "chimney fishing" to snare birds for protein. However, as sea levels rise continuously, the ground saturates and the house begins to submerge and flood from the basement upward.
During a severe flood sequence, bipedal aquatic leviathans with squiggly tentacles enter the lower levels of the house. Ruth recognizes similarities between these entities and ancient marine folklore, realizing they are ancient ocean dwellers rather than space aliens. When one of the creatures becomes injured and trapped inside the flooding home, Jason corners it with an improvised weapon. Instead of killing the creature out of fear or revenge, Jason lowers his weapon and spares its life.
Recognizing this act of mercy, the creatures dissolve the liquid barriers around the homes. The endless rain ceases, and the sky clears. The Delgado family builds a makeshift boat from house materials and sails out onto a completely transformed, flooded Seattle landscape. As they navigate the open waters, a crackling radio stinger broadcasts a voice saying "Hello?", confirming that other human survivors remain across the flooded world.