I find these guys so elusive. They always swim in the middle of the pond out of range of my 400mm. This guy was doing likewise, but dived under water only to resurface near me (before quickly swimming away again).
Canon 7D
Canon EF 400mm f/5.6L
1/1250 sec f/6.3 ISO 400
Crop for composition, levels, sharpening in CS6
NR on BG in Noiseware 5
I wish the head was turned just a tad more towards me, but he scurried off before obliging.