Convenient Censorship such as steam, hair and beams of light are often used in anime and manga to show naked characters while obscuring their "naughty bits".
There are various forms of convenient censorship but they all have the same purpose; they make certain anime scenes and manga pages acceptable when they otherwise wouldn't be. In recent years beams of light, steam and shadows have all become popular techniques, blocking genitals and nipples from view. In some cases anime disc releases come uncensored, arguably giving fans more incentive to buy the home version.