Hmm… good question. I don’t know yet. I thought Ocean Sim loops animation. 
Nope it doesn’t. Let me do some research.
Crap… I can’t figure out a way to loop it.
My suggestion is to make a new thread here asking how to loop an ocean simulation. Maybe someone here knows.
WAIT! FOUND A WAY.
Make a new ocean simulation in Blender. Get the settings you want, then when you are done with that do the following:
The time field should say “1”. Change it to zero, and then make sure you are on frame 1 of your animation. While the mouse cursor is over the time field, hit “I” on your keyboard. The time field should turn to a different color. Green I believe.
Then, move your frame slider to the half-point of your animation. Go to your time field, put in however many seconds into the animation the half-point is. (250 frames is about 10 seconds, so if there are 250 frames then you would put in 5) With your cursor over the time field, hit “I” again. Then move to the last frame of your animation, go to the time field, put 0 in, hit “I” again. Now watch your animation. See how your animation starts slow and then speeds up over and over? You can change that with the interpolation mode of your keyframed “Time” field. This is crucial. Now, bake the EXR’s.
Let me know if this works for you. 
I just tried it myself and it’s a bit weird. The loop is a bit obvious. It probably wouldn’t be a big deal if you had more frames, so it wouldn’t happen nearly as much.