The mobs ingame are meant to represent 4 of the main things that we do to ourselves to trigger cancer: smoking, drinking, sun exposure and stress ( that last one moves faster but yeh it needs a lot of work).
The question on the opening screen is all about, should you expose yourself to these things at all or jump into a place thats safer, but are you really living if you don't at least try these things (and blow them up).
The terrain far below was meant to represent a peaceful place to just wander, a place that we sometimes accidently fall into and then go, oh this is ok.
So in my stupid artistic perspective there are no sharks, crocs or redback spiders, just a choice, to remain in peace or dive back into battle.
I may have said too much :)