I'm a beginner.
I've done some practice few times on a longboard and didn't have any problems standing up and turning (thx to my snowboarding skills).
I decided to buy my stuff for carry on.
I got a 7' board (I'm about 1.78 tall) and around 60kg of weight.
I have some troubles when I lay on the board, before catching the waves.
Often the top of my board goes underwater when the waves comes, and if I carry on trying to catch it, the board just keep going down with the top part and I fall in the water.
I tried to move my center body position a bit back (so my feet are out the board now), but if I do that I can't catch the wave energy (or rarely tho).
When I used the longboard during a lesson, the instructor told me to keep the feet at the end of the board.
When I try on this shorter board I have this problem and I can't find any answers about how the body must be on a shorter board.
All suggestions are welcome

Thx!