It’s not that simple. Consider this document regarding the invalidity of the Mormon baptism.
The Form. …] The formula used by the Mormons might seem at first sight to be a Trinitarian formula. The text states: “Being commissioned by Jesus Christ, I baptize you in the name of the Father, and of the Son, and of the Holy Spirit” (cf. D&C 20:73). The similarities with the formula used by the Catholic Church are at first sight obvious, but in reality they are only apparent. There is not in fact a fundamental doctrinal agreement. There is not a true invocation of the Trinity because the Father, the Son and the Holy Spirit, according to the Church of Jesus Christ of Latter-day Saints, are not the three persons in which subsists the one Godhead, but three gods who form one divinity.
Therefore it boils down to whether it is a “real” Trinitarian formula or only an apparent one. I do not know what the case is for this denomination.
The Intention of the Celebrating Minister. Such doctrinal diversity, regarding the very notion of God, prevents the minister of the Church of Jesus Christ of Latter-day Saints from having the intention of doing what the Catholic Church does when she confers Baptism
Could it also be the case here? It is something that we (at least I) cannot address here, but could be.
The Disposition of the Recipient. The person to be baptized, who already has the use of reason, has been instructed according to the very strict norms of the teaching and faith of the Church of Jesus Christ of Latter-day Saints …] It does not seem possible that the person would have the same disposition that the Catholic Church requires for the Baptism of adults.
Thus, it boils down to the doctrine of this denomination and whether or not it hinders the form, the minister’s intention, and the recipient’s disposition.
I was not sure that salt water was valid matter, but I found this post shows that it is indeed valid.