Seto no Hanayome, Shinryaku! Ika Musume Recommendations
Mermaids and squid both come from the sea. This is MAL and that's enough to justify linking the two. Yes.
It's also worth noting that both series consist almost entirely of gagtastic slapstick comedy. Mermaid Bride has romance and haremish humour powering a hefty chunk of its jokes, where as Squid Girl has its titular heroine and is devoid of love-love... aside from a lesbian stalker. But those minor differences aside, these two are aimed at 100% the same crowd.
Fast-paced gag comedy featuring anthropomorphic girl living in human society. Ika musume traverse the shoreline trying to conquer humanity. Seto San somehow end up being a bride-to-be, not to mention that her house is a badass yakuza mermaid family.
Both shows have a good amount of comedy and are fun to watch. Plus each female lead comes from the ocean; with San Seto being a mermaid and Ika-Musume being a squid.
Another great masterpiece. Both the female protagonists came from the ocean. Both are funny and enjoyable.
Both contain very similar humor and settings. The stories are quite different in subject matter, but the mood is nearly identical. Seto no Hanayome is much more absurd and over the top in it's approach. Shinryaku! is much more grounded but still has many goofy moments.
Both series contain the fun entertainment that is met to amuse the viewers rather than a typical approach.
Both the main girl in the two series have aquatic features and are known to be quite energetic.
Overall, watch these two series if you want some great comedy with some drama.