I really liked this OVA too, it looked really good. And we got more diving scenes which was one of the reasons I was interested to the show in the first place.
I noticed that Teko's two friends in this OVA are voiced by the seiyuu who voiced Akari and Aika from Aria so I looked into it a little more and found that the mangaka is also the author of Aria and the director is the director of Aria. It really does have a similar feel to Aria at times, even though the setting is more normal.