For reference, I researched what moves Croconaw can use given your restrictions. I also deleted what moves I'm sure I couldn't get, and the results are as follows:
Shadow Rush (deleted after purification)
Focus Punch (difficult to use, requires victory over Pyrite Colosseum, which has Pokemon whose levels are above 50)
Hail (almost useless)
Hidden Power (provided it isn't Water-type)
Ice Beam (requires 4000 Poke Coupons, which means almost definite drudgery)
Iron Tail (Requires 4 victories in the Under Colosseum, which are slightly higher leveled than Pyrite.
So because of its incredibly narrow movepool (as well as having to put up with a Croconaw for 25 levels without evolving it), I'm going to have to reject Power. You will, however, have a reserved spot if you wish to try again.
My Challenge Compendium
Current Challenge: Colosseum Scramble
Status: Prologue is up!
Warning: When things heat up in a thread, I usually chicken out. I also have the tendency to overlook minor details at times.