Now that the Broodals are gone (already), it's time to explore more of the Lake Kingdom.
Here's some Hint Art for the Cascade Kingdom. Notice that there is one more rock formation on the picture on the right compared to the one on the left. Remember this for later.
Certain Power Moons can be found in more than one, but the way you'll be using to find it depends on which kingdom you go to when given a choice between two of them at the few points in the game where you'll have the freedom to do so. These Power Moons will be mentioned accordingly.
There is a seed in the spiky underwater tunnel. Talk to the Lochlady near the flower pot to get the seed to show up, then go through the spiky tunnel. It's easier to do this as a Cheep Cheep. Once you find it (and the four nearby Regional Coins), you'll need to switch back to Mario and take the seed back to the surface (to get more air) and back to the Water Plaza where you can plant it. The coin in the bubble will make it easier; save it for the journey back.
Power Moons
Lake Kingdom
4. End of the Hidden Passage - Use the Bouncy Flower at the Courtyard to get to a higher ledge with a zipper. Open up the wall with a zipper to find a hidden passage with a Power Moon.
10. Lake Kingdom Timer Challenge 1 - At the Courtyard area, there is a Scarecrow on a small plot of land. Throw your hat at it, then jump into the gap in the wooden blocks and keep ground pounding to get to the bottom fast enough to get this Power Moon.
11. Lake Kingdom Timer Challenge 2 - Warp back to the Courtyard Terrace after beating the Broodals and throw your hat at the scarecrow. Do a ground pound jump by jumping as soon as you hit the ground on a ground pound, and keep doing that to quickly get to the top and get this Power Moon.
15. Lake Fishing - In the Courtyard area, catch the big fish with Lakitu. You'll get a Power Moon.
16. I Met a Lake Cheep Cheep! - After you beat the Broodals, take a Cheep Cheep to the small land mass with the hole in the center and place the Cheep Cheep in the hole. The Lochlady will thank you for allowing her to see a Cheep Cheep up close, and you'll get a Power Moon.
18. Let's Go Swimming, Captain Toad! - Possess a Cheep Cheep and go down the long chasm in the Water Plaza. You'll find Captain Toad; talk to him for a Power Moon.
27. Found with Lake Kingdom Art - You'll need to find the Hint Art on the stairway leading up to the Courtyard area. Go to where the extra bone segment was located in the Hint Art and ground pound there. You'll find the Power Moon.
Luncheon Kingdom
47. Secret Path to Mount Volbano! - There are two ways to get this Power Moon.
If you went to the Wooded Kingdom first, then the Lake Kingdom, this Power Moon will be found in the painting in the pond in the Courtyard.
If you went to the Lake Kingdom first, then the Wooded Kingdom, this Power Moon will be found in the painting behind an iron block on the iron wall in the Wooded Kingdom, which can be reached atop the wall from the Station 8 checkpoint.