The biblical examples of baptism were done by immersion or being submerged briefly under water.
Jesus was baptized by immersion: (Matthew 3:16)
The book of Acts is full of examples of baptism by immersion: (Acts 8:38-39). Words such as “went down into the water” and “out of the water” give evidence that biblical baptism was by immersion.
Immersion best symbolizes death and new life which is the imagery of baptism. In Romans 6:3-5 we find that baptism is symbolic of death, burial and resurrection.