In reply to Dave:
My first one was a second hand Orca S2 that I scrounged. It gives you an understanding on fit and stops you spending a fortune on one.
Do you have anyone you could borrow one off. Some OW swimming locations allow you to hire them, sometimes even for a season, so that may be worth looking it thats an option where you live.
I used my S2 for a couple of years and loved it, but then upgraded to a new more expensive Aquaman, and the difference was quite noticable