We know that you'll be distracted by all of that Chris Hemsworth tussling-in-the-mud, but if you look closely and keep your eyes peeled at this Thor clip, you can just make out the Avengers archer watching the action from on high.
How do we know that figure obscured by darkness and rain is actually Hawkeye? If you look really, really carefully, you can spot the bow. Remember that scene in Predator where Arnold Schwarzenegger learns how to camouflage himself with the waterfall mud? This is kind of like that, if you add one pretty spectacular power kick.