Why is this the answer?

The answer is waterfall because this beautiful riddle uses clever word pictures to describe one of nature's most amazing sights. A waterfall is where a river tumbles down over a cliff or a rocky drop, falling straight into the water below. It is a natural wonder that has many special parts, and the riddle's four clues match them perfectly. Let's look at the first clue: "Bright as diamonds." Think about all the water splashing as it falls. When the sun shines on the tiny drops and the mist that floats up from the crash, they sparkle and glitter! Each tiny drop of water catches the light and shines brightly, looking exactly like thousands of brilliant, tiny diamonds scattered in the air. This sparkling spray is what makes a waterfall look so bright and shiny to our eyes. Next, the riddle says, "Loud as thunder." Have you ever stood close to a really big waterfall? The huge amount of water crashing down onto the rocks and the pool below creates a tremendous sound. It is not a soft, quiet sound like a peaceful stream; it is a powerful, booming noise that can be heard from very far away, especially after a heavy rain. That constant roaring sound is just as big and loud as the noise of thunder during a storm, making it truly dramatic. Then we have the line: "Never still." Rivers are always flowing, and that means a waterfall is always moving. The water is constantly pouring over the edge of the cliff, never taking a rest. It flows day and night, all year long, rushing over the rocks and down to the river below. A waterfall does not stop or sit still; it is always in motion, which is why the clue says it is never still. Finally, the riddle calls it "A thing of wonder." A waterfall is so powerful and so beautiful that it makes people stop and stare. It is an amazing natural place that reminds us how incredible the world is. The way the water drops from a great height is truly magnificent and awe-inspiring, which makes a waterfall a genuine thing of wonder for everyone who sees it. All of these special clues together point to the same spectacular natural creation.