Toby has always loved baths.... teh guy we got him from was a groomer so he liked getting his nails cut, hair cut, bathed,... ect.... i do give him a good rub down and massage his little body while i am working in teh shampoo, but he pretty much tells me when he wants a bath
you might want to close the shower curtain except for where you are when you are bathing him so he wont get out, and then speak to him in a soothing voice, or play soothing music, you should also make sure youre baby is nice and warm at all times, you dont want to associate a bath with being cold because that will backtrack your efforts