Communities of corals, sponges and other invertebrates, together with a unique mix of tropical and temperate fish species, have also formed in some areas.  The wide intertidal flats on the shores of Shark Bay support a unique community of burrowing molluscs, hermit crabs and other invertebrates. But the very foundation of Shark Bay's ecosystem is the seagrass - meadows and meadows of it!

Shark Bay has the largest area of seagrass and the largest number of species ever recorded in one place in the world. Whereas there is only one species of seagrass in most of North America and Europe, in Shark Bay there are 12 species, and, in some places in the Bay, nine can be identified in a square metre.

 The marine park and the scientifically-important seagrass banks form an important part of the Shark Bay World Heritage Area.

The marine habitats of Shark Bay Marine Park offer many shallow, but highly recommended, diving and snorkelling sites, The most renowned sites are at Monkey Rock and the wreck of the "Gudrun", rated by the Western Australian Maritime Museum as one of the State's best wreck dives. Fish species in the area include estuary cod, many species of brightly-coloured wrasse such as cleaner fish and green moon wrasse, scissortail sergeant, lined butterfly fish, varieties of surgeonfish and brightly-coloured angelfish.

The clear, calm waters of Shark Bay are a boating and fishing paradise. Boats may be launched from trailers at Nanga, Denham and Monkey Mia. Amateur fishing licenses may be obtained from the Department of Fisheries in Perth, Geraldton or Denham. Charter boats, fishing excursions and nature study cruises depart from Denham and Monkey Mia.

Boat owners are asked to be aware of the importance of avoiding areas where dugongs are feeding. These slow moving, gentle creatures are easily disturbed.