Abzu is designed for exploration. Many of its secrets, including fish pools and shells, are tucked away in less obvious locations. Always check behind large coral formations, inside small caves, and along the edges of the map.
Look for subtle visual cues: a slight glow, an unusual rock texture, or a small opening that seems out of place. Sometimes, following a specific school of fish can lead you to a hidden area. Don't be afraid to stray from the main path.