From a Romanian catechism article I've learned that in exceptional cases, a Deacon can perform a baptism, and in absolutely exceptional cases even a layperson can, given that the formula for being baptized in the Name of The Holy Trinity (The servant of God, etc.) is used.
However, if a Priest becomes available, then the rest of the prayers, Christmation and Holy Communion must be administered. Even sand, soil, etc. can be used when water is missing. From one source, if you don't use water, then you have to repeat the Baptism with water also if it becomes a possibility, but until then it is valid.