You know the LAKE. Steep descent in, steep ascent out, unforgiving, subject of the first Mountain Lake Landing Challenge.
Now for PART II
Explore the lake itself!
The Challenge: Go to the lake and dive down as far as you can. That's all.
You may:
a. build a sub and fly it to the lake
b. build a submersible plane
c. transport a submersible rover and drive it to the bottom
d. something else very cool I did not think of that is in keep