Doraemon Movie 45: Shin Nobita no Kaitei Kiganjou

Ten thousand meters beneath the sea, Nobita and his friends discover that Earth still hides a world humans have never truly explored. With Doraemon's gadgets, they descend into the deep and encounter a hidden civilization, strange creatures, and secrets connected to an undersea devil castle. What begins as an exciting expedition becomes a threat to both the surface and the ocean below, forcing the group into an adventure where escaping back to land is no longer enough.