Movements in swimming should be slow to fast. The hand will accelerate from the start of the catch through to the exit of the hand at the hip. The same thing happens above the water where the hand should enter with speed...or as my friend @eneyjones calls it...”punching the monkey” 🐵
This helps a lot in open water if the conditions are choppy.
I often see a ‘gentle’ or ‘timid’ entry causing the swimmer to lose momentum and rhythm in their stroke. Be assertive with your entry and ‘let it go’ aka don’t overly control it where you lose your momentum - this can help you swim faster.