When you repent, you surrender your serpent seed, which is your human will, that is death to your human will. And when you die you have to be buried, your human will have to be buried.
That is why there are those who said they have repented but still does their own will. It is because their human will did not really die, it was not really buried six feet under the ground. Their human will would come out of its grave and does it own will again.
Baptism is repentance first. When you repent, you surrender the serpent seed, you kill the serpent seed, and then after that, you have to be baptized because repentance is death, death to your human will and baptism is burial of your human will. So, after death, you have to be buried.