That feature is an outdoor hot tub. And it's a problem due to pug anatomy.
Thankfully, this hot tub sits well off the ground, and it also sits well off of the deck. There's no way that a short little guy like Liam could ever get in there. I don't think he could even jump in there, even if he wanted to. That means I don't need to do any prep here to keep Liam from drowning, simply because he'll never be able to reach the water line.
But I am still careful to keep him inside when the cover is off of the hot tub. He can watch me through the windows, but I don't want him coming near the water. If the tub wasn't so high, however, I think I would take the darn thing out. Fences and such would never keep out a determined pug, and I don't know how I'd live with myself if something happened to my dog in my hot tub.