Commento su Esodo 14:29

ובני ישראל הלכו ביבשה, all the while the Egyptians experienced all these problems and were drowning, the Israelites had been walking trough the sea as if it were dry land. The areas still being traversed by Israelites were not affected by the sea reverting to its originals state.

ובני ישראל הלכו ביבשה בתוך הים, but the Israelites had walked through the sea on dry ground. The reason the Torah states this fact a second time is merely to tell us that the Egyptians were aware of this fact and also of the fact that the sea had formed a wall for the Israelites, whereas they themselves went down deeper into the earth. This was fulfilment of the prophecy in verse 18 that the Egyptians would become aware of the true nature of G'd. It is worth reading Ibn Ezra's commentary on verse 27 where he lambasts the commentators who tried to explain away the miracle. He debunks the theory that Moses was well informed about the times of low tide and high tide respectively, whereas Pharaoh was ignorant of this and this is why he drowned with his army. The fact that the Israelites marched on dry land as described and did not merely wade through mud which had recently been covered by the sea, plus the fact that the Egyptians observed the waters forming a wall on either side of the Israelites made it clear that all of this had nothing at all to do with high tides and low tides.

ובני ישראל הלכו, all this while the Israelites had already completed crossing the sea while its bed was completely dry.