Hey, my son has this problem as well, but I think it's not that serious now because I tried the following:
1) Adjust the water the way your baby wants it. I used a submarine water thermometer (can be bought easily). There is a indicated mark saying that temperatue is "ideal" for babies. However, different babies prefer different temp (same as adults). So your job is to try out different temp and see if one temp makes your baby cries less
2) Babies are afraid of those "falling" feeling. You can buy a "net stand" to put in the tub to support your baby. Your gesture in holding the baby is the same, but the net stand provides additional support, the baby can actually feel that he / she is not being held in midair.
3) Before you put the baby in the tub, place a warm wet towl on her / his chest. They hate the feeling of being totally naked.
4) Talk soothingly to your baby. Audio comfort is quite important, it puts her in a calm mood
5) Choose the right time to bath the baby. Don't bath her when she's crying already. Bath her when she's in a good playful mood. Bathing can be a play thing.
6) When finish, take baby out of the water very slowly, keep talking to her and wrap her up quickly but gently.