I mean, Mermista talks as if she doesn't care about Sea Hawk at times, but everything I see about them shows that they are nevertheless each devoted to the other.
They are constantly together, and you can tell that they positively motivate each other.
They never fail to be there for each other when it really counts.
They may be a mess, but they are a solid couple, and I think their relationship is actually pretty healthy, the way they understand and relate to each other.
Glimmer and Bow are an amazing couple, too!
Very healthy and with a deep caring and a great history together as well.
But I do find Seamista a bit more fascinating.