swimming isn't my thing

I have a swimming test for ROTC today at 2pm. We are required to take one every semester, it is called CWST (combat water survival test). I suck at swimming because I cannot float for a long time. One of the main parts of the test I cannot pass is the five minute treading water portion. If I do not pass this test today, I am subject to not commission as an officer. This morning during PT, I had to take a last minute swimming lesson from an experienced swimmer, but I kept on drowning. I kept on panicing whenever water got in my nose or if I felt like I was going to drown. Then the instuctor sat me down and physically showed me how to properly float. The main thing I learned is I have to focus and relax when it comes to floating. So I took his advice and next thing you know, I was floating like a champ. The main problem now is my arms and legs are sore and tired. Floating took a lot of energy out of me. So wish me luck today and hopefully I pass that stupid test! Other than that, my week is going good so far!