Acts 27:22-24 (NIV)
But now I urge you to keep up your courage, because not one of you will be lost; only the ship will be destroyed. Last night an angel of the God whose I am and whom I serve stood beside me and said, 'Do not be afraid, Paul. You must stand trial before Caesar; and God has graciously given you the lives of all who sail with you.'Acts 27:30-31 (NIV)
In an attempt to escape from the ship, the sailors let the lifeboat down into the sea, pretending they were going to lower some anchors from the bow. Then Paul said to the centurion and the soldiers, "Unless these men stay with the ship, you cannot be saved."
Here in this dramatic story of the shipwreck that occurred on Paul's voyage to Rome, there is an interesting dichotomy. On the one hand you have Paul, getting a clear message from God through an angel that they would all be saved through the storm, not one person would be lost. On the other hand, you have Paul warning that they would perish unless the men stayed on the ship.
So which is it? If God had decreed that none would be lost, how could it be possible that a man's action would change that decree? Why the necessity to even warn about it? It looks like the free-will of man could spoil the sovereign will (declared and spoken in fact) of almighty God. God's promise was fulfilled but it was accomplished through Paul's warning and the choices of the people. God's sovereign will never negates human responsibility.