Retaining water!

How much water retention? Daily fluctuations are natural, and water retention isn't fat so manipulating your water weight is not going to make you lose fat faster.

So my first answer would be: is it water retention or just normal fluctuations?
Small scale water retention can be caused by a higher than usual intake of carbs and/or salt. But also by hormonal fluctuations, sore muscles...
And more severe water retention can be a medical issue.

If you have extreme water retention - such as body areas where you can press the bloating with a finger and see an indent that stays there a moment, swollen hands/feet, tight/stretched areas of skin - then see a doctor. It can be a sign of serious health issues.

Short of that, don't try to get rid of it. Instead, learn to understand and accept it.

Shifts in water retention are part of how a healthy body stays healthy. Our bodies know what they're doing. We need to let them do it. Trying to disrupt normal water retention shifts is a bad health choice. It can be ups and downs of a few pounds, and it can drop or add from one day to the next or even within a day. Sometimes it hangs around for a few days, maybe even up to a week or two.

One normal thing when pursuing weight loss is to drop a bunch of water weight in the first week or two (which many people misinterpret as entirely fast fat loss at first, even though only a small fraction is fat loss). Then, the body rebalances so that water retention goes up over the next week or few, masking the continuing gradual fat loss on the bodyweight scale. If you're early in the process (first month or two), stay the course with patience.

Even fast fat loss is only going to average a few ounces per day (2 pounds a week loss is around a quarter pound of fat loss per day). The water weight shifts are multi-pound . . . even in menopause, I've seen as much as a 6-pound shift from one day to the next, though 2-3 pounds is more typical for me).

One thing that can increase water retention is stress. A calorie deficit is a physical stress, even though we hope the end results will be good long term. If a person tries to lose weight very fast, they can increase their chances that water retention will mask fat loss progress on the scale. If you're trying to lose weight fast, consider taking a more moderate approach, which may not only reduce the tendency to water retention but have other benefits (to health, not to mention being able to stick with the process long enough to lose a meaningful total amount of weight).

Other common causes of water retention are new exercise (that water is needed for muscle repair/rebuilding) and women's monthly cycles.

There's more in this thread about the kinds of things that can trigger normal water fluctuations in the body, plus useful information about other sources of weight fluctuation:

https://community.myfitnesspal.com/en/discussion/10683010/the-weird-and-highly-annoying-world-of-scale-fluctuations/p1

Be sure to read the article linked in the first post.

On repeat: If you have signs of extreme water retention, see your doctor. If it's only a few pounds with no danger signs, understand it and learn to accept it, for the sake of your continuing good health.

Best wishes!