It's all about flexibility and coordination. Look up some hip flexor and leg stretches and do them religiously. Then watch some YouTube videos on the eggbeater technique and practice on dry land, just laying on your back , then practice in the water while holding the wall… then progress to timed sets in the water.

The ones I use are keens (super comfortable but not as durable as some) and Lowas which are more durable but more expensive. Another recommendations, Salomon’s they makes several boots that work well.