On the ceiling of the submarine

 The submarine dove into the underwater canyon a few kilometers down.
Tracy the captain had told his men to adjust everything for the pressure. As they descended further than they had before.
They searched the bottom of the canyon for somewhere to conduct their research from.
The oxygen had been contaminated somehow before it was installed in the sub.
So one by one the men and women on board began to faint.
The captain got himself an oxygen mask.
He then did the heavy work of changing the huge oxygen tank by himself. Usually a job for two men.
After that he waited to see if his staff would awaken again.
He spent the following hour drawing on the ceiling in one of the of the chambers inside submarine.
The more he drew, the sleepier he got. Until he fell asleep on the ladder he had used to get up there.
He woke, something was carrying him. he was on a stretcher.
He asked about his staff. All accounted for.
His writing was found. It exposed his last thoughts as the man believed he and his crew would perish.
They went from full sentences about his love of life, his family and the world. To short words. Then to one last word. Hope.