What are he best water myths monsters, creatures or gods and underwater worlds e.g. atlantis??
The first thing which springs to mind would be the pair: Scylla and Charybdis of Homeric legend. One of these dangerous beasts inhabited an area either side of a narrow channel. Scylla is probably the more entertaining of the two, Charybdis only manifesting herself as an enormous whirlpool. Scylla is described as a frightful monster with twelve feet and six heads, each with three rows of teeth. Below the waist her body was made up of hideous monsters, like dogs, who barked unceasingly. She stood there in utter misery, unable to move, loathing and destroying everything that came into her reach, a peril to all sailors who passed near her. Whenever a ship passed, each of her heads would seize one of the crew. Cheers.