Generally sperm count 40-200 million/ml with normal motility and morphology is required for pregnancy.Having a watery semen might simply be that u r ejaculating too often and if u need diet advice i would say eat foods like tomato rice, beans or dal plus plenty of protein becoz semen and sperms are protein and finally food high in zinc is important and good for producing good semen plus do intercourse as ur wife ejaculate becoz female ejaculation is a sign of achieving her orgasm.