Plymouth Brethren teach baptism by immersion, using the examples of the baptism of Christ and the baptism of the eunuch by Philip in Acts. They point to the language of Christ coming up out of the water and the eunuch going down into the water to support this claim.
They reject baptism as necessary for salvation, but proclaim that it is necessary for obedience to Christ. Some Plymouth Brethren assemblies will not allow Christians to partake in the Lord’s Supper if they have not been baptized, though this isn’t something I’ve encountered regularly. They argue that one does not need to understand the symbolism of baptism, but simply need to be baptized in order to be obedient. Thus it’s not unusual for small children to be baptized.
Infant baptism is rejected, as baptism is considered to be for Christians only, thus giving rise to the often-repeated title among the brethren as practicing “believers baptism.”