definately do some upper body resistance workouts for your upper body strength. my suggestion is high rep, lower weight workouts to build muscular endurance and strength. do alot of body weight exercises such as Dips (triceps and chest) pushups (triceps and chest) and pullups (arms and back) these will help with your pop ups speed and explosiveness, and for paddling strength and endurance, do lots of lateral and front raises, shoulder presses and upright rows. you also want to build your leg and core strength so squats, lunges, sit-ups, crunches to the side and leg tucks should help in that area, this will help with your movement and flexibility.
try to keep sets and reps to 10-15 reps and 5 sets for each exercise, this should increase muscular endurance. also consider buying some resistance bands, which are available at most sports stores for added resistance, if you dont understand how to do some of the exercises here, go to www.bodybuilding.com
where you can see vids of the exercises ive mentioned. any questions PM me.
hope that helps