What experience do you have doing breast augmentations with highly active surfer women? (Photo)

The best implant placement to achieve a longstanding natural result would typically be submuscular using a smooth round moderate profile silicone get implant. Once healed, the chest muscular strength should he very similar or exactly the same as Preop. You'll have to layoff surfing for at least 6 weeks. Consider the Sientra implant. 

I have no direct experience with surfers as such, but I have performed breast augmentation on high level sportswomen who rely heavily on their pec muscles: rowers, swimmers and one heptathlete, to name a few. The logical answer is always to go over the muscle, so the muscle is not affected and there is less movement of the implant during upper arm and shoulder movements. However, all of these women (and you too, judging from your photograph) are very lean, with very little body fat and relatively small breasts. Therefore, there is very little tissue to cover the implants in their location over the muscle. This means that the edges and surface of the implant may be more noticeable. Therefore, the decision you have to make is a compromise between two imperfect solutions. Postoperatively, my patients have been happy with their choice, whether over or under the muscle, having understood the compromise they were striking. 

The quick and easy answer is on top of the muscle but you are so thin you will likely see the edges of the implant. Make at least two consultations with experienced breast surgeons and get the options open to you explained thoroughly. Good luck!