Still, rationally thinking, which is presuming a lot in the situation, I can't find any real advantage to the two tourists of having the dive guide not try.
There reason she gave was "Stay with us because they are going to come to get our bodies" so I think they were beyond worrying about anyone's wellbeing :( What a nightmare.
I read it as "They are going to come to get our bodies so there is a chance we'll make it out of here alive if we just wait".