The theory, originally posted in a Reddit thread approximately ten years ago and recently revisited amid the buzz surrounding the live-action remake, presents a far more complex backstory for Lilo and Nani's parents, as well as social worker Cobra Bubbles, than the film ever explicitly offers.

So, Nani returns to the ocean to save Stitch and carries him back to shore underwater. It was a moment to show Nani’s strength as well as her love for both Lilo and Stitch. Plus, it was an excellent way to end this climactic moment.