up to our noses
I say this in my own name. So, I can’t blame anyone else for it.
There are several kinds of irrational fears. A fear of mice or birds is easy to recognize as irrational. A fear of fire, water, or heights is harder to deal with because there is a logical basis for the fear. There are stories of people who die in fires because they are terrified to use the fire-escape stairs.
The generation of men who were the decision-makers during the exodus from Egypt had all been thrown into water at birth and almost drowned. We know what happens to babies who are subjected to this kind of abuse. They become irrationally and intensely afraid of getting their heads under water. So, we can assume that all of the elders, all the leaders of Jewish people were irrationally afraid of getting their heads under water.
When the Jews were at the Yom Suf. It is instructive to understand what physical reality looked like. On one side was the world’s most feared army. They promised the Jews rape, murder, and pillage followed by a return to slavery. On the other side, was water. Their deepest and most irrational fear. I have trouble blaming them for wishing that they were back in Egypt.
Then, as the medrish tells us, Nachshon walks into the water up to his nose. Facing his fears to the point where he can say to Ha-Kodesh-Boruch-Hu: “I have faced my fears and done all that it is physically and spiritually possible to do. Your turn.”
Ha-Kodesh-Boruch-Hu split the sea and dried the seabed. In effect saying: “Okay Bnai Yisroel, proceed with your next step in growth.”
Then we walked down onto the seabed. There are arguments about how deep the water was, but it was certainly high enough to drown the Egyptians. So the walls of water were, at least, 15 feet high. We walked along towering walls made of what scared us the most. Think of the courage it took to be saved.
This also teaches us something else. Deal with your deepest fears. Face your hardest opponent, yourself. G-d will take care of the rest.
I find it appropriate that of all the various physical life skills there are, the one that the Talmud chooses to mandate for all Jews is swimming.