It hit the Throckmartin party on that island and they probably were all more or less delirious all the time; thought they saw things; talked it over and--collective hallucination--just like the Angels of Mons and other miracles of the war.

Somebody sees something that looks like something else.

He points it out to the man next him.

'Do you see it ?' asks he.
'Sure I see it,' says the other.

And there you are--collective hallucination.
"When your friends got it bad they most likely jumped overboard one by one.