This seems like a stretch of biological truth (to allow a salt water Kraken to inhabit a deep dark underground lake).
And yes biological truth is important in a fantasy world; but not at the expense of coolness.
And a Kraken inhabiting a deep dark underground lake is cool.
|Hey, where did she come from? Google.|
Anyway, in the DSG there is a picture.
Here it is.
Now, I love illustrations that speak to the text (or vice versa), and in the Lower Lake of Deepearth, near the center of the ceiling, a constant column of water spills from the drain in the Upper Lake. The water around this column is quite turbulent, but the rest of the lake is rather placid (Lake Placid - no, don't say it!)
Now, I'm not sure in the pic, that isn't some giant stalactite. But what if was that column of water draining from an upper lake? And what if there was a Kraken living in the depths? And what if one could take that ferry across that lake? Wow. And what if Lake Placid had been a good movie?
Gems we should take
1. Deepearth can be a very cool setting, especially with a Kraken that has somehow adapted itself to live in fresh water.