There was probably a large mixture of feelings among the crew as they watched the Endurance sink. To some of them, the entire event likely did not surprise them or move them much in any way because they had already lost hope the ship would survive and it would eventually sink. This can be seen when a few of the crewmembers, when told to abandon ship, had quit on their own (p. 3) while working at the pumps. If they had truly felt to continue working would have saved the ship, and with it their lives, they wouldnt have given up working. .
Also, it was impossible to prevent a certain amount of complacency as the men became increasingly accustomed to the c camp life. (p. 79) The quote shows the men had pretty much given up their hope for the ship, and had accepted their fate was on the ice. Had this not been so, the men would probably have been checking the status of the ship almost constantly.
A second feeling among the men might have been a simple feeling of wanting to deny the fact the ship was truly sinking and they were stranded out on the ice, perhaps simply left to die.
At the official lights out for the men, a good many men turned in earlier. (p. 82) This signified many of the crew did not want to face the reality of their situation, but try to escape from it as long as they could by sleeping away as much of the day as they were able.
Lastly, there was likely a feeling of devastation because the ship was going to be lost. The event was obviously not a joyous one, as they watched in silence, (p. 83) showing the bleakness of the situation. The reaction was also to the passing of an old friend who had been on the verge of death for a long time, (p. 84) which is often devastating but also a relief at the same time because the constant pain of the friend, or ship, had finally ended.