Romans 10:9,10..."that if you confess with your mouth the Lord Jesus and believe in your heart that God raised Him from the dead, you will be saved. For with the heart one believes unto righteousness, and with the mouth confession is made unto salvation."
The prayer alone is not what saves you, but it's what's inside your heart that does. When you are born again, you will have a changed heart and it will show in how you live your life. The Holy Spirit will lead you to a desire to be baptized; to declare that you have laid down the old life and risen up in the new, but baptism is not what saves you. The thief on the cross was saved by his faith. Jesus said to him, "Today you will be with me in paradise." There was no chance for baptism. Your prayer, if sincere from the heart, is what saves you. After that you should have a desire to do that which is right before the Lord. Your thankful heart will lead you to do good works to the glory of God. Revelation 3:16 is in reference to the church in Laodicea which developed an attitude of indifference to God. They were wealthy and didn't feel a real need for Him. Their lukewarm attitude is a heart issue.