Sounds like Simoun. The question is, if it’s any good as an anime.
Let me set the record straight. Umi Monogatari is nothing like Simoun. Simoun is (or tries to be) a tragic-but-beautiful story about ill-fated warriors. Umi, unless the writers intend a nasty surprise, is a lighthearted adventure story with magical girls.
Both have yuri overtones, but so do about half the anime series being broadcast now. That’s not much of a basis for comparison.