The two games do look mighty similar and have pretty much the same player objective. When people pointed that out in comments for a YouTube trailer of Aquatica, Ketera Software responded by saying the source code was "100% written from scratch."
This was two hours after Chen himself had seen the game and made the following Twitter post:
"I released flOw source for people to learn. I didn't expect to see it on iphone without quoting the creator http://www.ketara.ca/aqua.html."
Luckily, this scandal seems to have a happy ending. 1up.com contacted both parties for comment and received a conciliatory statement from Ketera — and now Aquatica's website reads: "Please note: Aquatica is an iPhone from-the-ground-up re-make (FAN VERSION) of the famous flOw game created by Jenova Chen of the ThatGameCompany fame. We deeply apologize for not properly crediting him earlier. Our mistakes were caused by naivety, not malice."
I'm pleased the situation was worked out so quickly — the longer a scandal festers, the harder it is for a game to get clear of it and be awesome on its own. And it is awesome to have flOw on the iPhone, even if it has a different name and isn't affiliated with Sony.
Hm. I wonder what Sony has to say about Aquatica?