Saline implants are made of a shell that is filled with a salt water solution. Specifically, this fluid is IV fluid which is identical to the fluid which flows into your veins when an IV is started in the hospital. Should the implant leak, the fluid will be harmlessly absorbed by your body. There is no pain or discomfort in fact one cannot feel the implant leak at all. Generally, when a woman dresses in the morning she may notice that one breast is somewhat smaller than the other and by the end of the day it is generally clear that the implant is leaking because the breast has noticeably decreased in size.
This is not an emergency. Simply contact your plastic surgeon and have the implant replaced within the next couple of weeks. If the implant is replaced in a short period of time, it is a simple matter of putting a new implant in the same pocket. If one waits too long (a month or more), the pocket may begin to decrease in size. Then it becomes a greater matter to reopen the implant pocket to create enough room to replace the deflated implant. This may require a partial or complete removal of the pocket capsule.