When a member of the reptile species gets a boner in the water and tries to play it cool by laying in a plank-like fashion.
(Note: never insult a Southern Floridian Alligator with drift wood... you'll poke your eye out.)
Jason: I went down to the beach and saw the Geico Gecko doing the backstroke and he looked more like a shark!
Hal: Mad driftwood?
Jason: Reptile driftwood fo' sho'!