YEh I can totally relate to this, especially through the summer flat spells
How old are you???
I have been surfing for 20 years or so and am approaching 30 fast

later on this year. If I hav'nt surfed for a few weeks(rare) I can usually get my paddle power and fitness back over a coupla days If im in the water for at least 5 hours a day.
Usually takes a pretty good swell though for me to be that motivated though.
As long as ur eating well, stretching regulally and dont smoke you should be able to keep up.
I recently started going to "spinn class" on the bikes at the gym with my chick.
A great work out that really hammers ur whole body believe it or not. Good perv too



.Smash a few sets of sit ups, push ups and a jog or a swim every few days and ur styling. I noticed a real differernce.
Hope this helps get ya buff
Good luck