Koombana Bay is the sheltered side of Bunbury and the reason many visitors come to the city: about 90 bottlenose dolphins live in and around the bay, according to Tourism Western Australia, and the Dolphin Discovery Centre on the foreshore runs interaction and swim programs. For snorkellers, the bay offers calm, clear-ish shallow water that is protected from the Indian Ocean swell by the Bunbury peninsula and harbour breakwaters.

A regional holiday guide lists Koombana Bay as a beginner-friendly snorkel with dolphins, schools of fish and rays over a shallow sandy and seagrass bottom. Underwater it is a gentle muck-and-sand dive rather than a reef: expect stingrays and eagle rays on the sand, schools of small fish, crabs and seagrass fauna. The chance of dolphins passing close by is the main attraction, but wild dolphins should never be chased, touched or fed; the Discovery Centre's supervised programs are the way to get close.

The site suits families and beginners wanting an easy, safe swim and a chance of dolphins, and it is a sensible fallback when Back Beach is too rough. Scuba adds little given the depth and visibility. Boat traffic from the nearby marina and ramps means snorkellers should stay close to shore.

Dive-specific information is limited, so depths are indicative.

Geographe Bay is unusual on the WA coast because it faces north, so the prevailing south-westerly swell and sea breeze that close the ocean coast are largely blocked by Cape Naturaliste. That shelter, plus the warm Leeuwin Current, is what makes the bay's reefs, jetties and wrecks diveable for much of the year, and why winter north-westerly storms are the main thing that shuts it down.

Koombana Bay is on Koombana Drive on the eastern (bay) side of central Bunbury. Park at the Dolphin Discovery Centre or the Koombana foreshore car parks and walk onto the beach. Swim and dolphin-interaction programs are run by the Discovery Centre; independent snorkellers enter from the beach away from the Centre's interaction zone.

Bunbury has a local dive shop (Coastal Water Dive) for fills and hire.

Sheltered from the ocean swell by the Bunbury peninsula and breakwater; calm in most conditions except strong northerly and north-westerly winds. Summer is the dolphin-swim season. Visibility is modest because of the sandy bottom and nearby estuary outflow, especially after rain.

General pattern in Geographe Bay: sheltered from south-westerly swell by Cape Naturaliste; summer mornings are calm before the afternoon sea breeze, while winter north-westerly fronts roll swell and chop into the bay and reduce visibility for several days.

Snorkel from the beach over the sand and seagrass, watching for rays and dolphins, and stay clear of boats and the Discovery Centre's interaction area. Snorkellers should stay within easy reach of the exit point and swim with a buddy; scuba divers at these depths need no safety stop but should ascend slowly and surface near the float.

Dolphin Discovery Centre runs dolphin swim and eco cruises in season; no scuba operator - self-guided snorkelling. Nearest dive services: Octopus Garden Dive Charters and Coastal Water Dive in Bunbury; Swan Dive in Busselton.