The term, "baptized into Moses" in 1 Corinthians 10:2 gives us a lucid idea of what Paul meant by being "baptized into Messiah." It says nothing of the physical body of Moses.
Rather Israel had submitted to his "sphere of influence" as God gave him authority.
That is the kernel-truth of being baptized into Messiah, that a new believer enters His realm of authority, where His name rules. With a careful review the context also reveals a wider meaning for baptize than only immerse.
Many assume this verse is evidence of immersion in water. The walls of sea water and covering by the cloud are thought to have fully compassed Israel. But it would appear there were two open ends of the liquid corridor, one through which Israel exited and one through which the Egyptians entered. Not exactly an immersion.
Beyond that, were they surrounded by water into submission to the authority of Moses? In fact this relationship was not generated in the hearts of the Israelites simply by being surrounded in water.
The Torah describes how the nature of the Israelites changed after they passed through the midst of the sea. By the way, Paul was writing specifically to the Corinthians telling them the events of the Torah had been written for their admonition. Therefore it is only natural that we carefully examine the passage in the Torah.
30 Thus the LORD saved Israel that day from the hand of the Egyptians, and Israel saw the Egyptians dead on the seashore.
31 When Israel saw the great power which the LORD had used against the Egyptians, the people feared the LORD, and they believed in the LORD and in His servant Moses. Exodus 14:30-31 (NASB)
They came to realize the authority of the LORD and Moses after they saw the Egyptians dead on the shore. The Lord fought with both the cloud, Exodus 14:24-25, and the sea, Exodus 14:26-27 and these events caused the people to submit, not being surrounded.
In this baptism we see irresistible influence on the Israelites by apprehending the great power of God against the Egyptians. They did not fully believe till they saw the dead Egyptians, some time after they had passed through the sea.
Cloud and sea were forceful instruments of influence which made the Israelites change their opinion, baptizing them into - radically submitting them to - Moses.
Surely, by way of contrast, the Egyptians were "immersed" in the cloud and sea far more thoroughly than the Israelites, but they were not "baptized into Moses," they died.
The prepositions used in this passage support the idea of the instrumentality. In 10:1 the Israelites were hupo, under the cloud, and passed dia, through the sea. In the following verse they were baptized eis into Moses en by the cloud and en by the sea.
οτι οι πατερες ημων
παντες υπο την νεφελην ησαν
και παντες δια της θαλασσης διηλθον,
και παντες εις τον μωυσην εβαπτισαντο
εν τη νεφελη και εν τη θαλασση
As has been seen, en can mean "in," however it was a very flexible word and "in" was not its only meaning. Here it indicates instrumentality with the understanding "by means of" or "with."
The Israelites were not in the cloud they were hupo, under it. Neither were they in the sea they were dia, through it. They were also eis, into Moses, but not "into" the cloud or the sea.
The use of en for both cloud and sea speaks of joint influence, not a similar physical situation. The prepositions hupo, dia and eis make that clear.
Rather, after Israel saw the cloud and sea used as instruments to fight the Egyptians they were compelled to believe everything Moses was telling them about the LORD.
The fathers were baptized into Moses - vitally united with his authority - by means of the cloud and by means of the sea. Contrary to what is often taught, this verse lends no support for a supposed universal Christian water baptism.