Try higher 频率, slow down when becoming expert.
Never try to give too much 幅度.
Make sure you do NOT try to stick your arms/head/shoulder
too high. If you do, you naturally push your hip/legs under
water.
Try to do smooth medium pace kicks, approximately 2
kicks (up down, up down) with in one cycle (breathing).
At the begining, if your feet still sinks, try to
do it faster. Start fast,
Try to roll your upperbody, but control rolling of your
lower body.
Lastly, when you are comfortable, try to IMPROVE BY
"SLOWING DOWN": Key to freestyle of slow pace but low glide. World class
swimmer can finish 25 meters in under 10 strokes
and breathing under 5 times. So control body straight
line gliding is the most important part.