Probably depends on your provider.
I had Telstra data coverage everywhere in the Whitsundays, using a dedicated mobile data box that sat on the nav table. However my Optus mobile coverage was patchy, especially to the east of the big islands, but it worked at Whitehaven. I heard some complaints that coverage was lost even to the east of Hamilton, but unsure of which provider they were using.

In my experience with Vodafone is..... you're having a laught!!

But I love Vodafone in the CBD!

This is a good resource...

www.vodafone.com.au/network/coverage-checker

stupid said..
Just wondering if the brains trust knows if there is coverage on the inside of hazel wood island ? Near chalkys or a little to the north?
tia.

If you sail from Chakys towards Toungue Bay, to the north of the shallow area, you will get coverage. There is also some coverage outside Tounue Bay towards Esk Island. This from 2015 so may have improved?

Yeah mate, got a freshie. In Brisbane now working on getting her kitted out for offshore adventures in 2018.

Just wanted to ask, kind of in the vein of the topic, is / are there internet solutions available for offshore (assume satelite)...that anyone is or has employed.?