Atra du evarinya ono varda.
In my opinion, Splash could indicate that the user Pokemon is frail and weak and without much power. Look at Magikarp and Hoppip, for example. Both of them learn Splash by default. Magikarp is, of course, Magikarp, and Hoppip gets blown away by the slightest breeze.
In the spinoff games such as PMD however, Splash does 5 damage to both the user and the opponent, so it's essentially both somewhat useful and useless at the same time. xD