Heading north from Kalbarri there is a noticeable change in the environment. On land, the landscape becomes very arid with a noticeable jump in the air temperature. Big towns are gone and the road is dotted only by the occasional homestead and roadhouse. Permanent drinkable water is hard to find. Sealed roads are confined to the major highways and much of the coastline is inaccessible, dominated by large cliffs with little road access.
While south of Geraldton the tourist trade is focussed on summer beachgoers, further north the roads are deserted in summer, thanks to the sometimes oppressive heat and the December fly plagues. Even the tourist signs talk about a “rugged beauty”. Effectively, you are in the desert. Without a private boat, you will be confined to the few places offering charter services, presently that is Denham in Shark Bay, Exmouth and Coral Bay at Ningaloo. All these depend on adequate numbers of passing divers to warrant launching a boat, the Winter tourism peak season is the time to go. The weather is also much more agreeable.
At sea, the numbers of temperate species are low at Shark Bay and drop even further as you travel north. At the same time the tropical species begin to dominate.
While the north has a big tide range, the tides south of Exmouth are not very significant and the tide range is only about 0.8M on a spring tide. Inshore areas are usually free of currents with only offshore areas being susceptible to moderate wind generated currents of usually less than one knot. Swimming conditions are safe on the not too frequent calm days with low swells. Like much of WA, get started early before the afternoon sea breeze stirs up the water.