The first place in Australia to be designated a World Heritage Area (in 1991), Shark Bay is a pretty unique place, home to the oldest lifeforms on earth, 10,000 dugongs (sea cows), shore fed dolphins, and beaches made entirely of shells.
The oddly named Monkey Mia is home to a nice beach, though there are plenty of those around Western Australia, and more uncommonly wild dolphin feeding. Every morning there are 2-3 feeds for several families of dolphin in the area. Started in the 1960s accidentally by fisherman, it now attracts 100,000 people a year. Personally I thought it was an open water Sea World, and though there are plenty of rules to try and mitigate the impact on the habits of wild animals I wasn’t entirely convinced.
The oldest continuous lifeform on the planet, with fossils dating back 3.5 billion years, Stromatolites are microbes that have formed these 6,000-9,000 year old structures. They only remain in six places in the world, five in Western Australia, and one randomly in the Bahamas. The contrast of red rock and turquoise blue waters was pretty special.