Uhm... Sounds like ur too young to be doing that anyway. Especially since u know absolutely nothing about how a female gets pregnant.
Because your penis would probably still have live sperm in the urethra from the previous ejaculation, if any pre=ejaculatory fluid got into her body (which it could have done, since it kind of oozes out of the tip when you get an erection) it could have carried sperm into her body. Whether you "stuck it in halfway" or stuck it in all the way, if there was sperm in the pre-ejaculate that didn't have contact with the salt water (or even if it did, if the water was body temp) there is a chance of her getting pregnant. It will now depend on what time of her menstrual month it is, because to get pregnant she also needs to be ovulating, and that only happens once a month.