Hi Liam,
For distance and fuel usage, feel free to do some research into common types of boats and small water craft engine types.
For example, a quick Google search gives an approximate distance between Saibai Island and Thursday Island of 151 km. Similar could be done for fuel consumption.
It’s worth noting that the Torres Strait Island communities are a seafaring people, often traveling between islands and Papua New Guinea. You’ll be able to map out distances and make some calculated assumptions to support your design!
Cheers,
Anthony
Anthony Brady