Makes me so glad I changed up from my Watermaster to a Journey…14' Hewescraft - That's the second rattlesnake I've seen in this lake (same one your buddy had those two close encounters). I float tube in lots of lakes and rarely think about a reptile swimming up to me thinking I'm an island.
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This snake was wind drifting rather than swimming as the water was cold, only a few weeks after ice off. His drift was pretty close to a line on an anchored pontoon* boat.
* Similar to your buddies pontoon........
Dave