I assume Atomix was referring to one of the comments ("That said, it seems like there's an awful lot of tunnels for the sake of having tunnels, which, coupled with the speed of movement, is reeeeeally annoying really quickly.") rather than the main review, as the main text didn't have that critique.
That comment was me. Hi.

And what I meant by it wasn't tunnels vs. open ocean, but rather the distance between Point A and Point B being made arbitrarily lengthy. There was a lot of "ok, so you go down this tunnel, around the corner, past three armored fish, around another bend, down a long hall, around the hair-pin turn and... dead-end at a door you can't open yet. Return trip time..." where it could have been simply "ok, so you go down this tunnel, around the corner, past three armored fish and dead-end at a door you can't open yet." In another game, where the scenery was less compelling, that kind of rather pointless distance would be a major drawback. In Aquaria, it's an annoyance but one that can be lived with.