The Ocean Etude is such a beautiful piece. Listen to Rachmaninoff op 23 no 7 prelude - the beginings sound near identical.
Anyway, I love this piece, and have played it at a few concerts. 80 BPM is B.S. 80 BPM might be the speed at which you take your fastest arpeggio up and down, but there can be some rubato, and you need time to jump up and land down on your next set of bass notes.
I've done a good amount of the Chopin etudes (op 10 no 1, 2, winterwind, revolutionary, about 9 more) and for me, the Ocean Etude was definitely the hardest.
I did op 10 no 1 when I was in 8th grade, and had no problem, yet I did this etude in late highschool, and had major trouble getting it comfortably and up to speed.
The beauty of it is, when you have it down, you HAVE IT DOWN.
It can be braught back in a matter of days or even hours.