The Mermal Magic has a lot of great new features.
They are similar to regular Hatchimal CollEGGtibles in that they come in a case which you need to break (or hatch) by rubbing the purple heart until it turns pink.
Different in that these creatures come in a glitter shell (rather than an egg) and have fish and sea creature features such as fins and mermaid tails. Some also have accessories like surf boards and floaties.
There are even some that look like crabs, fish and seahorses and they are a lot more colorful.
Once they are hatched place them in warm water to see their special features change colors. To change them back either put them in cold water or just let them dry.
Overall I think these are better than the regular Hatchimals since they are more interactive and the fun is no longer just hatching them.