The sentence you wrote is almost correct! Here is the original sentence:
Elephants love to play with water, using their trunks to splash.
To make it clearer and grammatically correct, you can say:
Elephants love to play with water by using their trunks to splash.
This means elephants enjoy playing with water, and they do this by using their trunks to splash water around. Adding "by" helps connect how they play with water.