This is a bmp and is not the same image as the one in the gallery.
One of a series (Watermark level xx) in which it gets steadily harder to solve the puzzle, though there is a common theme to them all. The size and difficulty of the cache hide varies throughout the series. There is also a passphrase in each puzzle which will be some help with the next puzzle in the series. It is strongly recommended that you solve the previous level before tackling this one.
The commentary is encoded in a similar fashion to ROT13, but instead of moving on (encoding) or back (decoding) 13 places, the move on (encode) or move back (decode) is defined by repeated copies of the passphrase - A=1 position, Z=26 positions.
EG if the passphrase is "C'a d", then use "CADCADCADCAD..." or 3,1,4,3,1,4,3,1,4... to shift the text. So "watermark" is encoded as w+3=z, a+1=b, t+4=x, e+3=h, r+1=s, m+4=q, a+3=d, r+1=s, k+4=o which is "zbxhsqdso". There is an online decoder available now.
qmi lsclqnoontz plt aneajr rr hbr xbay bhchtk ft fs ajxslzfsy ftctf 01, qny oly mw xvy ffns jahry. nhz'mi meei hi ytpy ugvjhs mt gfsh clsg. jmfb sdb si nhz'mi wijpwmr yislt ph ndh rvzm mwjclzfuwic, zd sdn'qm kjim xc uyxp tcck hibxyifsk cs hyyq zco lopn xgkporecmch gt vgy. ttpcal bfihsvi.
This cache is a 600mL food box. The First To Find trophy went to IceColdUK.
Good hunting. You may also be interested in my other caches.