I've been compeating as a diver at my college and we've been doing some great workouts that really transfer over to paintball.
Core/Abdominals
One-Leg Extensions
(With forearms and feet on mat, lift one leg at a time and hold for 5 seconds. Touch down and repeat. Hold the last one on each leg for 10 seconds) 2 sets of 10 each leg
Hollow-Body Holds (Face Down)
(Feet and hands on mat in stretched-out push-up position. Go as low to the mat as possible) 2 sets, 30 seconds
Hollow-Body Holds (Face Up)
(Lay on back, squeeze stomach, legs and butt, lift legs, arms and shoulders while pressing lower back to the ground.) 2 sets, 30 seconds
Back Single Leg Lifts
(Lay on stomach with arms stretched overhead. Lift then lower one leg at a time. Hold last one for 10 seconds) 2 sets of 25 each leg
Back Extensions
(Lay on stomach with arms stretched overhead. Lift then lower both arms and both legs at the same time.) 2 sets of 25
Tuck-Ups 2 sets of 25
Pike-Ups 2 sets of 10
Hanging Tuck-Ups 2 sets of 15
Hanging Pike-Ups 2 sets of 10
Legs/Plyometric Circuit
Squat Jumps
(Hands on hips bending to squat potion followed by jumping and landing softly back in a squat position.) 2 sets of 15
Steps-Up
(Step up with one leg onto at least 12-inch bench, bring knee up and jump off of foot that is stepping up. Land softly back on same foot and bring feet together onto the floor.) 2 sets of 10 each leg
Mountain Climbs
(Starting in an extended lunge position, jump to identical position landing on other leg.) 2 sets of 20, switching legs
Ankle Extensions
(Stand on one leg with heel hanging off the edge of something. Holding 15 to 20 lb dumbbell, lift to tip-toes, then lower heel.) 2 sets of 10 each leg
Arms/Shoulders
Handstands
(Against wall) 2 sets each direction, holding 15-20 senconds
Handstand Push-Ups
(Against wall.) 2 sets of 5 to 10
On top of this 2-3x a week (takes about an hour each time) we're supposed to do 30min to an hour of Cardio on top of that. Biking is the prefered method since it also builds leg strength, but running or swimming are also benificial.
Diving is pretty similar to paintball with respect to the quick explosive movements and the need for strong legs and core.
Hope this is helpful...
-Micah