Baptismal Regeneration is the belief that baptism is essential to salvation and that it is the means by which God actualizes the forgiveness of sins for the believer. It says that we are regenerated at baptism--not at faith. Baptismal Regeneration is incorrect.
Baptism is a covenant sign that signifies our union with Christ that occurs by faith. It is a public declaration.
Paul said that he came to preach the gospel - not to baptize (1 Cor. 1:14-17). If baptism were essential to salvation, then Paul would have included it in his standard practice and preaching of the salvation message of Jesus, but he did not. (See also Col. 2:10-11)
For more information on this see Is Baptism Necessary for Salvation?