The artist used Unity to set up the effect.
Game Developer and Tutorial-Maker Cyan, known for creating incredible shaders in Unity, has recently presented an impressive waterline effect created for the artist's latest stylized ocean shader. According to the creator, the effect was set up by generating a mesh at the camera near plane, using a technique similar to the one showcased by Technical Environment Artist Staggart Creations back in 2021. Much like the artist's previous projects, the effect was created with Unity.
Back in September, Cyan also demonstrated a neat coastline water shader, created by reconstructing the world position from the depth texture and using the Y-axis of this reconstructed position in a sine function to produce the waves. You can learn more about it here.