Summary: 1) A New Trail (Isaiah 43:16–17), 2) A New Thought (Isaiah 43:18), 3) A New Thing(Isaiah 43: 19a), and 4) A New Tender (Isaiah 43:19b-21)
Have you ever gone on a journey not knowing where exactly you would end up? When Lisa and I went on our honeymoon, we left home with a general vicinity in mind, but the route and ultimate destination was to be determined. All we knew is that we loved each other, we were going together and we would enjoy the experiences together.
For the people of God in Isaiah 43, Israel was presently in captivity in Babylon, but there was a new horizon before them. God promises that his people will be released from exile through a new exodus. He was their God and He desired to show forth His glory through them in their deliverance. As glorious as the exodus from Egypt was, a new journey was before them even greater than before. All these events recorded in chapters 40–55 of Isaiah are believed to have occurred from the middle of the sixth century (Crossway Bibles. (2008). The ESV Study Bible (p. 1233). Wheaton, IL: Crossway Bibles.)
We don't know what exactly lies before us, but we too are in captivity. Sin holds us back from everything God wants and the full delight He desires for us. He promises great and marvelous works, doing it in ways we can't even imagine. But we need to discern the path to take, with a God-centered mindset.
Isaiah 43:16-21 shows us who this God is that goes with us towards this New Horizon. For a people in captivity, God shows: 1) A New Trail (Isaiah 43:16–17), 2) A New Thought (Isaiah 43:18), 3) A New Thing (Isaiah 43: 19a), and 4) A New Tender (Isaiah 43:19b-21)
1) A New Trail (Isaiah 43:16–17)
Isaiah 43:16–17 Thus says The Lord, who makes a way in the sea, a path in the mighty waters,  who brings forth chariot and horse, army and warrior; they will lie down, they cannot rise; they are extinguished, quenched like a wick: (ESV)
In the context of Isaiah 43, this is a prophetic prophecy which looks beyond the overthrow of present enemies to the return home for a people of God. The description is obviously related to the exodus. But it is not so much the events themselves we are invited to reflect on as it is the power, the love, and the dependability that the Lord demonstrated in those events (Oswalt, J. N. (1998). The Book of Isaiah, Chapters 40–66 (p. 154). Grand Rapids, MI: Wm. B. Eerdmans Publishing Co.).
• In considering a way forward, we must have a true destination in mind. It does no good to merely seek to eliminate present difficulties, if we fail to figure out what we hope to gain. In essence we can gain everything we might immediately desire and not achieve any lasting godliness. In God's economy, we often must persevere through difficulties to achieve true holiness and success in His kingdom.
In verse 16, God reminds His people of what he did at the time of the Exodus from Egypt, providing them with a path through the sea and at the same time destroying the Egyptian army. The 6th century B.C. is also a time when naval power becomes a military factor. In the Aegean and eastern Mediterranean, powerful Athenian and Phoenician fleets serve Egyptian and Persian interests in seeking control of the shipping lanes. Yahweh claims control of forces at sea, as well as those on land. But eventually they will all be extinguished like a wick (Watts, J. D. W. (1998). Isaiah 34–66 (Vol. 25, pp. 134–135). Dallas: Word, Incorporated.).
Please turn to Joshua 3 (p.179)
To bring assurance of the greater future deliverance He will bring through His Servant, the Lord reminded Isaiah’s readers of His deliverance of their ancestors from Egypt (Ex. 14:16, 21, 26–28; Josh. 3:13) (MacArthur, J., Jr. (Ed.). (1997). The MacArthur Study Bible (electronic ed., p. 1021). Nashville, TN: Word Pub.).
Joshua 3:1-17 Then Joshua rose early in the morning and they set out from Shittim. And they came to the Jordan, he and all the people of Israel, and lodged there before they passed over. 2 At the end of three days the officers went through the camp 3 and commanded the people, “As soon as you see the ark of the covenant of the LORD your God being carried by the Levitical priests, then you shall set out from your place and follow it. 4 Yet there shall be a distance between you and it, about 2,000 cubits in length. Do not come near it, in order that you may know the way you shall go, for you have not passed this way before.” 5 Then Joshua said to the people, “Consecrate yourselves, for tomorrow the LORD will do wonders among you.” 6 And Joshua said to the priests, “Take up the ark of the covenant and pass on before the people.” So they took up the ark of the covenant and went before the people. 7 The LORD said to Joshua, “Today I will begin to exalt you in the sight of all Israel, that they may know that, as I was with Moses, so I will be with you. 8 And as for you, command the priests who bear the ark of the covenant, ‘When you come to the brink of the waters of the Jordan, you shall stand still in the Jordan.’ ” 9 And Joshua said to the people of Israel, “Come here and listen to the words of the LORD your God.” 10 And Joshua said, “Here is how you shall know that the living God is among you and that he will without fail drive out from before you the Canaanites, the Hittites, the Hivites, the Perizzites, the Girgashites, the Amorites, and the Jebusites. 11 Behold, the ark of the covenant of the Lord of all the earth is passing over before you into the Jordan. 12 Now therefore take twelve men from the tribes of Israel, from each tribe a man. 13 And when the soles of the feet of the priests bearing the ark of the LORD, the Lord of all the earth, shall rest in the waters of the Jordan, the waters of the Jordan shall be cut off from flowing, and the waters coming down from above shall stand in one heap.” 14 So when the people set out from their tents to pass over the Jordan with the priests bearing the ark of the covenant before the people, 15 and as soon as those bearing the ark had come as far as the Jordan, and the feet of the priests bearing the ark were dipped in the brink of the water (now the Jordan overflows all its banks throughout the time of harvest), 16 the waters coming down from above stood and rose up in a heap very far away, at Adam, the city that is beside Zarethan, and those flowing down toward the Sea of the Arabah, the Salt Sea, were completely cut off. And the people passed over opposite Jericho. 17 Now the priests bearing the ark of the covenant of the LORD stood firmly on dry ground in the midst of the Jordan, and all Israel was passing over on dry ground until all the nation finished passing over the Jordan. (ESV)