I allow my patients to get into the shower at 48 hours postop, and into a bath 3-4 weeks if the incision is healed. Just a word of caution, your abdominal skin is still numb and be careful not to injure your skin with the hot water.
I generally allow my patient to shower 48 hours after surgery, even with the drains. As far as taking a bath where the incisions are immersed, I generally would like my patients to wait about 4 weeks before doing that, that includes going into a pool as well.Good luck. Make sure your discuss this with your plastic surgeon as every patient is different and every surgeon has their own protocol.