Once again, I am going to profess my love for atmospheric scientists and the cool internal wave images they keep sending me. Click on the pic to an animation of giant internal waves propagating away from the mouth of the Amazon River!
UPDATE: I forgot to add that it is unclear what causes these waves. Most likely they are tidally generated as they are seen all year long . But there is a paper that argues that since they are so different from other tidally generated internal waves, other mechanisms might generate or modify these waves .
Hattip to my atmos BFF Steven Cavallo for the link.
 C. Jackson. Internal wave detection using the moderate resolution imaging spectroradiometer (modis). J. Geophys. Res., 112(C11):C11012, 11 2007.
 P. Brandt, A. Rubino, and J. Fischer. Large-amplitude internal solitary waves in the north equatorial countercurrent. Journal of Physical Oceanography, 32(5):1567–1573, 2012/10/24 2002.