I'm a big Pokemon fan among many other things and many of the older seasons of the anime had the use of scuba gear. Team Aqua from Pokemon Advanced actually used scuba gear, but also drysuits in the episode called A Three Team Scheme. It was pretty cool so i decided to have an MLP character wear one of these suits while underwater. However, I tweaked the suit for Twilight a bit to make it more fit her physiology. I might think to add flippers to her back legs later down the road.

Images used:

Twilight image: https://www.deviantart.com/andoanim.....Twilight-Sp...

MLP Underwater Background: https://www.deviantart.com/loladrea...../MLP-Underw...