They are common. Fish for them on Routes 103, 105, 106, 107, 108, 109, 110, 115, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133 & 134, Dewford Town, EverGrande City, Lilycove City, Mossdeep City, Pacifidlog Town, Seafloor Cavern, Shoal Cave and Slateport City.
Wailmer evolves at Level 40.
Evolve Wailmer
water!
The only way the Wailmer will move is that you must clear out the Team Magma Hideout north of the Wailmer. After you achieve this, the Wailmer and the man training the Wailmer will disappear.
Level 40
Level 35
Yes but its rare.
In Pokémon Ruby, you can obtain a Wailord by first catching a Wailmer, which is the pre-evolution of Wailord. Wailmer can be found in the water routes, particularly Routes 110 and 132. Once you have a Wailmer, level it up to level 40 to evolve it into Wailord.
Evolve a wailmer at level 40.
Catch a wailmer and get it to level 40.
Off the east coast of Lilycove.
Wailmer evolves at level 40