Artist's comment:

Patreon patron reward for NialloftheNine. It's also a gift for who's an awesome artist in his own right. Several years ago NC did series of pony pics inspired the Kantai Collection. In particular he did Twilight Sparkle as submarine .
Now apparently NC's avatar, or one of his avatars, is a potted cactus wearing a Arizona State baseball cap and sunglasses. But for this piece I was asked to put the cactus in a wet suit and scuba gear. Unfortunately spines and wet suits don't play well together. Hopefully Twilight will be able to rescue the fellow.