You can buy some stretch cords. Attach them high so you can use them in a straight, normal swim posture, only standing instead of lying. You can even stand on one leg and combine a kick with a pull movement to get your core also involved in a more swimlike manner.
Watch how elite swimmers move when seen from pool bottom to watersurface and mimic that movement, using a mirror.
Repeat until that movement becomes your automatic movement.
Right before going to the pool, repeat the right movement on dryland until your muscles become painfull, sore and exhausted.
Now go to the pool ,swim and feel if your movement mimics the painfull dryland movement.
If thats the case you have a chance you usually make the right movements in the water.
If the movements feel very different in the water, you use different muscles so you dont make the right movements when you swim.
Its a crude method, but without self footage or a good coach it can be usefull.