Tear drop/anatomical implant under muscle? Skinny 35 year old mum of 2. Advice?

Your breasts will have a naturally augmented look if you select the right implant. A natural aesthetic breast tends to have a gentle slope in the upper part, peaking at the nipple and a rounded lower part of the breast. This can be achieved by using a natural shaped or anatomical shaped or tear drop shaped implant. These are implants that taper towards the top (towards your collar bone, on your chest) and are fuller at the bottom (towards your abdomen), giving the breast a more natural shape. A large implant can result in a rounded appearance in the upper pole, rather than a gentle slope. But if this is what you desire, then this is what you may need to go for.

Round implants do give more upper pole fullness and you could potentially get a "stuck on" appearance. This can particularly be an issue if you do not have much of your own breast tissue. But if prominent breast in the upper part is what you desire, then these implants may be for you. There is a reason why the tear drop implants are called 'anatomical' implants - it is because they resemble the anatomical shape of a natural breast!

An anatomical profile or tear drop profile or shaped implant can potentially rotate, but this is dependent on the technique and when properly done, this is not usually an issue. On the other hand, round implants are uniformly round and full in all directions, so rotation doesn't affect the shape of the breast.
Placing the implants under the muscle may affect your
strength at pulling down on a rope. Although the Lats muscles are the main
contributors to this action, the Pecs also contribute significantly.
During the placement of the implants under the muscle, the muscle is released
from its attachment to the sternum in the lowest part. Although this does not
significantly reduce muscle strength, it may matter in someone like you who is
in to extreme sports! The other issue you might end up with because your very
strong Pecs is that of animation of implants, although this is surgical
technique dependent, the risk wound be more in your case. Animation of implants
is when your implants move up when you tighten your Pecs. In view of this you
might be more suitable for having the implants placed above the muscle, but you
do need to be prepared for the implants being more visible and palpable due to
lack of breast or fat tissue to cover them if you don't have much. For optimal outcome, please consult a fully qualified plastic surgeon, who has specialist qualification in plastic surgery 'FRCS Plast' after having being trained adequately in the field of plastic surgery, is registered on the 'Specialist register for Plastic surgery' with the General Medical Council and has been considered competent enough to be a member of the 'BAPRAS' (British Association of Plastic Reconstructive and Aesthetic Surgeons) and 'BAAPS' (British Association of Aesthetic Plastic Surgeons) at the least.

Thank you for the question.  
These days there are a variety of breast implants available; the variety of breast implant available raise a lot of questions from women considering breast augmentation surgery. Personally, I think that for most patients considering breast augmentation surgery, careful selection of plastic surgeon and careful communication of goals, far outweigh the specific type of breast implant utilized (when it comes to the success of the breast augmentation procedure).
Anatomical breast implants were designed to better simulate the natural breast shape; the problem with these implants is that if they shift or rotate, the entire breast will change shape as well. This change in breast shape may require further surgery to correct. Round implants, under the hand, can shift or rotate without changing the shape of the breasts. Overall, I find that beautiful outcomes can be achieved with the use of round saline or silicone gel breast implants for the vast majority of patients.
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of words such as “natural” or "C or D cup" etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery, after the use of temporary intraoperative sizers.
I hope this helps. Best wishes for an outcome that you will be very pleased with. 

It would be difficult to determine which shape and size would be best for you without an in-person examination. Your best course of action is to schedule an appointment with a board-certified plastic surgeon. The shape and type of implants depend on factors like chest wall measurement, tissue elasticity, and your desired results.