It’s about merpeople researching the past (humans).  I liked how suspenseful it was and how I could picture the characters in my head as I was reading along.  I felt like it was really easy to visualize the large cave that they were in.  I want to know how they are moving about.  Do they walk?  Do they swim?  I would suggest sticking to one verb in terms of how they move, since both are used in the story.  I would also like to see some sort of resolution to the story, like a more concrete ending rather than everything being left up in the air.