Umi Monogatari: Anata ga Ite Kureta Koto, Nagi no Asu kara Recommendations
An obvious similarity - sea themes! People from the sea interacting with people of the land, plus their interpersonal relationships.
Water plays a large role in both of these series as well as mythology. Both have some level of interaction with character in and outside of the water and the bonds/friendship they may create.
Both of them are light hearted series that become more serious towards the end. They're about people who live in the sea interacting with people who live on land and facing a supernatural disaster.