Reading mermaid magic descriptions always gives me this weird sense of vertigo—like the rules are just beyond human grasp. Their spells aren't just about moving water; they're about manipulating pressure, light, and currents to create effects we'd need complex machinery for. A lot of authors skip the physics, which is fine, but the ones who lean into it, like in 'The Deep' by Rivers Solomon, make the ocean feel alive and hostile. The magic there isn't convenient; it's a trade-off, often tied to memory or breath. That kind of system makes the underwater setting matter, not just a backdrop.
I've noticed a trend where mermaid spells get lumped in with general water magic, which feels lazy. Their magic should reflect a culture that evolved in three dimensions, with no 'up' or 'down' as we know it. Illusions based on refracted light, sonar-based communication spells, enchanting bioluminescence—that's the good stuff. When it's just generic hydrokinesis, I lose interest fast.