Rashi (on 14:27) explains that the Jewish people saw the Egyptians since G-d flipped the Egyptians when the waters covered them. According to this idea, even though the Egyptians were initially on the bottom of the Yam Suf, because G-d flipped them, they were on the top of Yam Suf. Rashi (on 14:30) also writes that afterwards the sea threw the Egyptians on the shore. According to Rashi both the Jewish people and the dead Egyptians were on the shore.
The Bekhor Shor (on 14:30) varies this slightly. He writes that the bodies washed up on the seashore, though this would have had to have occurred relatively quickly for the Jewish people to have seen them.
Bibliography:
Cassuto, Umberto (1883-1951), 1967, A commentary on the book of Exodus, Jerusalem: The Magnes Press.
Chavel, Hayyim Dov, 1993, Commentary of the Ramban, revised edition, Jerusalem: Mossad Harav Kook.
Sarna, Nahum (1923-2005), 1991, The JPS Torah Commentary: Exodus, Philadelphia: The Jewish Publication Society.
Ibn Ezra rejects this approach since he argues that it cannot be that the Egyptians ended up on the shore because 15:12 records that they were swallowed by the earth. However, Luzzatto defends Rashi's approach and suggests that 15:12 only means that the majority of the Egyptians were buried at the bottom of Yam Suf. Still some of the Egyptians floated or were thrown to the seashore and these are the bodies that the Jewish people saw.
A similar question exists with the word ve-yenaer in 14:27, which Rashi translates as flipped. Luzzatto explains the word that G-d caused the Egyptians to fall into the middle of sea and this understanding is followed by the JPS commentary (in Sarna, 1991, p. 74) that translates the end of 14:27 to mean that G-d hurled the Egyptians into the sea. Similarly, Cassuto (1967, p. 171) writes that end of 14:27 means that the Egyptians were thrown "into deeper waters." How could the Egyptians be hurled into the sea if they were already at the bottom of the sea when they entered the sea. It must be that some Egyptians were on the shore, but how can this be? To answer this question, we need to ask another question, what did Pharaoh's army who was chasing the Jewish people consist of, only chariots or also foot soldiers?
It would be unlikely that Pharaoh would only have taken chariots. Surely he would have mustered whatever forces he had, and this would have included as many infantry soldiers as possible. 14:6 records that he took his chariot and his people, and then 14:7 records that he took his charioteers with him. Are the charioteers in 14:7 the people referred to in 14:6 or were there two groups, the people who were his infantry, and the charioteers, his crack force? Similarly, 14:9,17 refer to Pharaoh's horses, chariots and forces (chelo). Is the term forces, a general term for the charioteers (as in 14:4?) or an additional force? Ramban (on 14:28) writes that chel is not the charioteers but the people referred to in 14:6. This force would be the infantry that accompanied Pharaoh to fight the Jewish people, and this understanding can answer our questions.
14:23 records that the charioteers chased the Jewish people, which meant going into Yam Suf. They were the quicker force and they entered the Yam Suf first, while the infantry remained on the sea shore. 14:24,25 record that the charioteers got stuck in the middle of Yam Suf. 14:26 then records that G-d told Moshe to hold his arms over the sea, and the waters would cover the horses and the horsemen.
14:27 records that when Moshe raised his arm over the sea, the waters began to return, and the Egyptians began to flee towards the water. This fleeing is difficult to understand since normally one flees away from the danger but here the Egyptians were fleeing towards the danger, the water. Maybe the fleeing Egyptians were the infantry who were still on the shore that G-d caused them to flee towards the water. 14:27 ends that G-d hurled the Egyptians into the midst of the sea, and this can refer to the infantry who were "fleeing" towards the water. Thus, G-d caused them to run towards the water, and then G-d hurled them into the water. Accordingly, 14:27 refers to two separate actions. One, the waters to start returning to its course, and two, G-d caused the Egyptian infantry that was on the seashore to enter the sea. The infantry forces entered the sea as the waters were returning, which meant that many of them were at the top of the water. 14:28 then records the culmination of the two processes from 14:27 that the water covered all the Egyptian forces.
14:28 is usually understood to refer just to Pharaoh's charioteers who were chasing the Jewish people. With this approach, the phrase "chel Pharaoh" is referring to the charioteers, and the words "after them" is referring to the Jews as in 14:17,22. Yet, both 14:17,22 follow verses which refer to the Jewish people, and hence one can understand that the reference to "after them" in these verses is to the Jewish people, but in 14:28 there is no prior reference to the Jewish people. Also, the term "chel" was not mentioned in 14:23 which records which of Pharaoh's forces chased the people into Yam Suf.
A similar question exists with the word ve-yenaer in 14:27, which Rashi translates as flipped. Luzzatto explains the word that G-d caused the Egyptians to fall into the middle of sea and this understanding is followed by the JPS commentary (in Sarna, 1991, p. 74) that translates the end of 14:27 to mean that G-d hurled the Egyptians into the sea. Similarly, Cassuto (1967, p. 171) writes that end of 14:27 means that the Egyptians were thrown "into deeper waters." How could the Egyptians be hurled into the sea if they were already at the bottom of the sea when they entered the sea. It must be that some Egyptians were on the shore, but how can this be? To answer this question, we need to ask another question, what did Pharaoh's army who was chasing the Jewish people consist of, only chariots or also foot soldiers?
It would be unlikely that Pharaoh would only have taken chariots. Surely he would have mustered whatever forces he had, and this would have included as many infantry soldiers as possible. 14:6 records that he took his chariot and his people, and then 14:7 records that he took his charioteers with him. Are the charioteers in 14:7 the people referred to in 14:6 or were there two groups, the people who were his infantry, and the charioteers, his crack force? Similarly, 14:9,17 refer to Pharaoh's horses, chariots and forces (chelo). Is the term forces, a general term for the charioteers (as in 14:4?) or an additional force? Ramban (on 14:28) writes that chel is not the charioteers but the people referred to in 14:6. This force would be the infantry that accompanied Pharaoh to fight the Jewish people, and this understanding can answer our questions.
14:23 records that the charioteers chased the Jewish people, which meant going into Yam Suf. They were the quicker force and they entered the Yam Suf first, while the infantry remained on the sea shore. 14:24,25 record that the charioteers got stuck in the middle of Yam Suf. 14:26 then records that G-d told Moshe to hold his arms over the sea, and the waters would cover the horses and the horsemen.
14:27 records that when Moshe raised his arm over the sea, the waters began to return, and the Egyptians began to flee towards the water. This fleeing is difficult to understand since normally one flees away from the danger but here the Egyptians were fleeing towards the danger, the water. Maybe the fleeing Egyptians were the infantry who were still on the shore that G-d caused them to flee towards the water. 14:27 ends that G-d hurled the Egyptians into the midst of the sea, and this can refer to the infantry who were "fleeing" towards the water. Thus, G-d caused them to run towards the water, and then G-d hurled them into the water. Accordingly, 14:27 refers to two separate actions. One, the waters to start returning to its course, and two, G-d caused the Egyptian infantry that was on the seashore to enter the sea. The infantry forces entered the sea as the waters were returning, which meant that many of them were at the top of the water. 14:28 then records the culmination of the two processes from 14:27 that the water covered all the Egyptian forces.
14:28 is usually understood to refer just to Pharaoh's charioteers who were chasing the Jewish people. With this approach, the phrase "chel Pharaoh" is referring to the charioteers, and the words "after them" is referring to the Jews as in 14:17,22. Yet, both 14:17,22 follow verses which refer to the Jewish people, and hence one can understand that the reference to "after them" in these verses is to the Jewish people, but in 14:28 there is no prior reference to the Jewish people. Also, the term "chel" was not mentioned in 14:23 which records which of Pharaoh's forces chased the people into Yam Suf.
Instead, maybe one can understand "chel" in 14:28 just as we suggested in 14:9,17 that it refers to Pharaoh's infantry, and then the reference to "after them" in 14:28 is that Pharaoh's infantry followed the charioteers into the Yam Suf. With this understanding, 14:28 means that the waters covered the charioteers and all of Pharaoh's infantry, so that there was no one left in the Egyptian army. (See Rashi and the Rambam on 14:28 and Chavel's (1993) notes to the Ramban with regard to the lamed prior to the word col.)
14:29 then records that the Jews were marching in the sea, which as noted by the Ibn Ezra, means that while the Egyptians were drowning, the Jewish people were still in Yam Suf.
When the Jewish people reached the seashore, they were saved, 14:30. They were the only ones on the shore, and from the shore they saw the Egyptian infantry floating on the sea. Eventually these Egyptians fell towards the bottom, as indicated in 15:5,10. The people would not have seen the horses, chariots and charioteers who had drowned at the bottom of the sea, and did not rise to the top. In the end all of Pharaoh's army was at the bottom of the sea and there they were buried, as recorded in 15:12.
14:29 then records that the Jews were marching in the sea, which as noted by the Ibn Ezra, means that while the Egyptians were drowning, the Jewish people were still in Yam Suf.
When the Jewish people reached the seashore, they were saved, 14:30. They were the only ones on the shore, and from the shore they saw the Egyptian infantry floating on the sea. Eventually these Egyptians fell towards the bottom, as indicated in 15:5,10. The people would not have seen the horses, chariots and charioteers who had drowned at the bottom of the sea, and did not rise to the top. In the end all of Pharaoh's army was at the bottom of the sea and there they were buried, as recorded in 15:12.
Bibliography:
Cassuto, Umberto (1883-1951), 1967, A commentary on the book of Exodus, Jerusalem: The Magnes Press.
Chavel, Hayyim Dov, 1993, Commentary of the Ramban, revised edition, Jerusalem: Mossad Harav Kook.
Sarna, Nahum (1923-2005), 1991, The JPS Torah Commentary: Exodus, Philadelphia: The Jewish Publication Society.