...The mention of Kimberly and making pictures IN the local streams brought immediately "crocs" to my mind.
I am sure that you are around with experienced guides and tour operators...
I can assure you that no-one will be blundering around in ignorance on this trip.
Apart from anything else the operators of the yacht on which they will be travelling will not allow anyone to do anything dangerous.
Being attacked by a crocodile is exceedingly bad for business!
In the Kimberleys many rivers can be entered from the ocean and navigated for variable distances.
The limiting factor governing navigation is waterfalls.
Below the falls = saltwater crocs.
Above the falls = no saltwater crocs.
However, ultimatedly local knowledge is all and this knowledge will be readily available .
I have travelled and photographed in the Kimberleys, and other parts of northern Australia, where Estuarine Crocodiles are found on many occasions and being 'croc-smart' is not hard - if you have half a brain.
I have also spent plenty of time in Africa where Nile crocodiles (no less dangerous in the context) and Hippopotami (arguably even more problematic) abound with no incident.
Common sense wins out every time.
I confidently predict all members of the PODAS trip returning with life and limb intact - as far as the 'Saltie' threat goes!