Inspired by Wilson's post w/the shark, here goes
What is your personal best, most awesome act of nature seen on a stream, pond, lake etc. excluding the salt.
MINE: While fishing Farrington lake several years ago, along the lilly pads throwing a super fluke into the pads, I saw a mother duck trailed by several new hatchlings. All of a sudden, there was the most explosive swirl of water and a large pike surfacing nearly out of the water to engulf the small baby bird. The mother and remaining chicks headed to shore and I launched too many casts in that direction in an effort to get a similar strike.
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But, seeing this was way too cool.
My second: finding a snake with a bluegill in the mouth at a local pond here in NJ, both nearly expired. Caught them both, released the snakes grip, and both swam away