Or could just be the old "switch" issue well known in the Cessnas on certain floats where the gear is electrically operated by a small normal on/off switch. if you are distracted by something on take off and forget to retract it, and since it is so small you do not notice it. then maybe the sun on the lights , and here you go.. But I do not know the/this Beaver actual system and if you feel the gear is down during cruise. On the big Cessna's , at least the one I flew, you didn't..