Should I change my board?

Hello everybody!
I started surfing last summer. I’m really addicted to it!
Mostly I go to La Jolla Shore and sometimes other beaches in San Diego area.
3-4fts hight normally.
I’m using a Quiver Therapist 6’6” 20 2 3/4 Short board
I’m 5’9” tall 125lbs. I’m really light.
I have been to the water roughly 50 times.
I can ride some waves when it’s not too big.
However, when the waves are huge I can’t even paddle out because I have problem duck diving. Feel so hard to push the board deep into the water.
Is it because of the measurement of the board I’m using?
If that’s really the reason, what size of short board do you recommend me to get for this summer?
What does water tight mean?
Thank you very much!!!
I started surfing last summer. I’m really addicted to it!
Mostly I go to La Jolla Shore and sometimes other beaches in San Diego area.
3-4fts hight normally.
I’m using a Quiver Therapist 6’6” 20 2 3/4 Short board
I’m 5’9” tall 125lbs. I’m really light.
I have been to the water roughly 50 times.
I can ride some waves when it’s not too big.
However, when the waves are huge I can’t even paddle out because I have problem duck diving. Feel so hard to push the board deep into the water.
Is it because of the measurement of the board I’m using?
If that’s really the reason, what size of short board do you recommend me to get for this summer?
What does water tight mean?
Thank you very much!!!