on water.....

Water. You have God-given right to be in it, no matter where it is, or what its colour, or its smell. You know you have this right, particularly when your human throws a stick or ball into the pond, lake or sea. If your human is slow to throw an item in, ensure you enter the water first, to signal that you wish to play this game.
(Simon Whaley - One hundred ways for a dog to train its Human.)