Cyclicpushover and Telstar, it is standard procedure to have the gear down for over water ops (and land to for that matter) as the main floats are mounted on the inside of the main gear doors and if you go into the water it assures a smooth activation of the floats , as an explosive link goes off between the door and the strut to allow the door to come up against the airframe and inflate the float, the gear down also helps stabilise the A/C in the water by acting like a keel and also lowers the center of gravity to also help with stability, you do the same with Super Pumas and similar a/c for the same reasons.