In Pokemon Sun and Moon, ‘Splash’ has been regarded as one of the most useless moves Therefore, people are now associating this move with Magikarp.
On the other hand, a new move called “Z-Moves” has now been introduced in Pokemon Sun and Moon. “Z-Moves” can only be used once in a battle after you have the right item.
The official Pokemon Sun and Moon site describes the move as:
There are two conditions for performing Z-Moves: a Pokémon must learn a move of the same type as a Z-Crystal, and it must be holding the corresponding Z-Crystal.
After the addition of the “Z-Moves,” people have now data mined that the new move can be paired with normal moves including ‘Splash’ to boost the effect.
In the video below, pro Pokemon player pokemon_PhD has shown how the “Z-Splash” boosts a monster’s attack thrice in a single time:
little vid of Z-Splash in action just to give you a better idea how Z-status moves work. pic.twitter.com/OejBLuuGPp
— Mike S. (ΩDonut) (@pokemon_PhD) November 10, 2016
Now, Players are also trying to figure out other possible competitive uses for Splash with characters like Mimikyu, Poliwrath and legendaries like Lunala, Solgaleo etc.