This is a beautiful dream and God is giving you such clear instructions in it. The simple interpretation is this the water is the spirit realm and also the word of God. Your life is going to be so much easier when you stay in the realm of the spirit and do things God’s way. In the shallow water that is dirty means that you are getting spiritual advice from the wrong source (dirty water, shallow water). You need to stay in the deep. When you are on land you are operating in the flesh and out of your own strength. Hence, you are tired. You get lost and you are earnestly trying to get back to the water because you know that you are striving when you do anything in the flesh. The people on the land are the people also operating in the flesh. They are giving you worldly advice and not godly wisdom and you know it is not correct.
There are other swimmers in the water because the truth is there are other Christians who are alongside you swimming as well. Their attitude in the water is their attitude in the spirit realm.
Obstacles are to be expected. God will guide you through, over, and around all of them if you stay in the spirit and close to the Spirit.
Read these scriptures
1 Corinthians 9:24