I've kept/bred/hatched/raised water dragons for over 15 years. I keep them in glass cages (with screen lids) that are longer than they are high. The cage is divided so that about 2/3rds of it is "land" and 1/3 is water. The two areas are divided by a glass dam about 8" high (for adults). I have a drain in the water area and a tap below the cage so that I can easily drain it. I make sure that the water isn't deep enough to drown the dragon.
I have a long linear tube UVB light running along the back part of the lid and a basking light at one end (over the "land" part of the cages). Basking temperature for adults is in the high 80's to low 90's. For hatchlings I keep the temperatures more moderate (low to mid 80's) I use cypress mulch as a substrate and have several branches for them to sit on. When there is a female in the cage, I put in a place for her to lay eggs.
I feed the hatchlings small crickets twice a day. I feed the adults an assortment of insects every second day. I also feed them an assortment of greens (dandelion, kale, collards, endive, escarole, mustard greens, etc.) and veggies (carrots, sweet potatoes, squash, zucchini, sweet red pepper, etc.) and a small amount of fruit (apple, pear, melon, berries, etc.). I use this for babies and adults.
I dust the insects the same way I do for the chameleons and I also put a powdered calcium on the "salads".