This bite-sized horror story offered nothing new to the table, but proved a fun distraction. Sadly, any fan of the horror genre will be able to guess where the whole this ends up about halfway through, but given the quick pacing, that in and of itself doesn't ruin the outing.
The mangaka's attempt to marry the innocent visuals of the mermaids (all cast as girls in school swimsuits) with the horrific behavior of the characters only succeeds halfway. The impressive images of gaggles of girls swimming through the air and between the walls of the class rooms certainly adds an other-worldliness to the work, but I felt that the actual horrific visuals came up sorely lacking. That said, the manga did put a slightly refreshing spin on an old theme.
If you're a fan of horror and a fast reader, this one is worth the 20 minutes it will take you to read it.