Being a Cornish girl

and having never been on a surf board in all my 27 years, I decided that it was about time I did something about this so I am off to Lanzarote for a weeks intensive surf school in October. The object is being able to take full advantage of staying with my parents in future for cheap surfing holidays.
The one question I have though is does anyone have any advice on what sort of exercise I should be doing before I go. I currently go to the gym about 2 times a week but want to know if there are any fitness areas I should be concentrating on.
Any help or advice would be appreciated!!
Thanks
Sarah