I would like to play in a water world with deep oceans and islands everywhere, not just occasional ocean biomes. I have looked for a good seed, but nothing really shows up. I am wondering if there is a way I can hack to flood an entire world. Is there an effective way of raising the water level across the entire world?
Try out the Bukkit plugin called Terrain Control. It features the ability to change the water height by modifying the config. However, you will have to run a Bukkit server on your local network to use it.
As of snapshot 14w17a, it is now possible to customize the water level ingame. When creating a new world, this can be achieved by clicking
More World Options..., changing the
World Type to
Customized, and then selecting the
Customize button. Here, you can change the sea level by moving the slider that says
Sea Level, as well as many more options.