trouble duck diving + bottom turn backside

My duck diving technique is good and my depth is okay.
but when I get out in head high conditions and the wave breaks right on me then I
get really tumbled because I don't duck dive deep enough.
I'm 5'3 120
1. How do I duck dive really deep? whenever I try to duck dive my deepest
I go down deep and then I go backwards and up really slowly and even sometimes I will lose my board.
2. another question, I surf decent frontside but a lot of times when I go backside and I bottom turn for a re-entry
I bury my rail and lose all of my speed or fall.
here's a video of me surfing
https://www.dropbox.com/s/se63g9orkjms2 ... 6.mp4?dl=0
Thanks !
but when I get out in head high conditions and the wave breaks right on me then I
get really tumbled because I don't duck dive deep enough.
I'm 5'3 120
1. How do I duck dive really deep? whenever I try to duck dive my deepest
I go down deep and then I go backwards and up really slowly and even sometimes I will lose my board.
2. another question, I surf decent frontside but a lot of times when I go backside and I bottom turn for a re-entry
I bury my rail and lose all of my speed or fall.
here's a video of me surfing
https://www.dropbox.com/s/se63g9orkjms2 ... 6.mp4?dl=0
Thanks !