improving balance

hi all,
haven't surfed much before, just a few hours in total, but loved every second
recently back from tenerife, where i had a lesson from k16 surf, managed to leave a part of my skin on the reef there, but still enjoyed it, however i found a bit of a problem.
last time i surfed i managed to balance a little, even stood at one point:-)
this time, i think i was on a slightly shorter board, a foam one still, but a little shorter, and i found i was having real difficulties even balancing when lying on the board, fell off every time i tried to sit, although i did manage to ride some waves in, didn't manage to stand, just kneel.
Anyone any advice on how to improve my balance, or could it just have been down to the different board?
cheers
haven't surfed much before, just a few hours in total, but loved every second

recently back from tenerife, where i had a lesson from k16 surf, managed to leave a part of my skin on the reef there, but still enjoyed it, however i found a bit of a problem.
last time i surfed i managed to balance a little, even stood at one point:-)
this time, i think i was on a slightly shorter board, a foam one still, but a little shorter, and i found i was having real difficulties even balancing when lying on the board, fell off every time i tried to sit, although i did manage to ride some waves in, didn't manage to stand, just kneel.
Anyone any advice on how to improve my balance, or could it just have been down to the different board?
cheers