Tennis Court takes its name from a level, open patch of white sand that looks like a court from the surface, ringed by coral bommies and reef. It is one of the nine named moorings on Flynn Reef and is used mainly by Pro Dive Cairns on its liveaboard itineraries, where it provides a change of pace from the walls and pinnacles elsewhere on the reef. The dive is essentially an edge dive: most of the interest is where the coral meets the sand.

Blue-spotted lagoon rays and cowtail stingrays rest on the sand, garden eels sway in colonies further out, and goatfish and sand-sifting gobies work the bottom. Around the perimeter, bommies of hard coral host the usual Flynn mix of fusiliers, parrotfish, butterflyfish, damsels and coral trout, and turtles often rest on the sand or at the base of the coral. Moray eels are common in holes on the bommies.

Because the site is open and fairly shallow it is bright, easy to navigate and good for divers working on buoyancy or navigation skills, and for photographers who want rays and sand-dwellers against a clean background. At night the sand comes alive with hunting cuttlefish, crabs and shrimp, and sleeping fish tuck into the bommies. It is not one of Flynn's headline sites, and published detail is thinner than for Coral Gardens or Tracey's, but it is a pleasant, relaxed dive and rounds out a multi-dive stay on the reef.

Snorkellers can see rays and turtles from the surface in good light.

Boat access only. Cairns day boats leave from the Reef Fleet Terminal (1 Spence Street) and the neighbouring Marlin Marina on the city waterfront, with check-in between about 7:00 and 8:00 am; most operators run transfers from city and northern-beaches accommodation, and there is paid parking near the terminal. The run of about 57 km out through Trinity Inlet and across the lagoon to Flynn Reef takes around 80 minutes on a fast catamaran and noticeably longer on slower dive boats or into a south-easterly chop.

Tennis Court is one of the Flynn moorings listed by Pro Dive Cairns and Cairns Dive Adventures; it is used mainly on liveaboard itineraries and occasionally by day boats. Enter from the stern platform.

The prevailing south-east trade winds (typically 15-25 knots from April to September) are what limit Cairns outer-reef diving: above about 25 knots trips may be cancelled, and exposed eastern moorings are used only in light winds. Summer northerlies are gentler but make north-facing moorings choppy. Box jellyfish and Irukandji are present from about November to May (stinger suits on every dive), and the cyclone season runs November to April, when a system in the Coral Sea can close the reef for days.

Visibility drops after heavy rain and strong winds; spring is usually calmest and clearest. The flat sandy bottom is sheltered and calm in moderate south-easterlies; visibility over the sand can drop if a swell stirs it up.

Descend to the sand flat at about 12 m, then work around the edge where coral meets sand, looking for rays and garden eels. Visit the surrounding bommies for coral trout and turtles, then return across the shallower coral to the mooring and do a safety stop at 5 m.

Pro Dive Cairns – liveaboard (occasional); Silverswift – occasional day-trip mooring on Flynn; Flynn is also worked by Silverswift, Passions of Paradise and the Pro Dive Cairns liveaboard; the mooring used on any day is chosen by the skipper according to wind, tide and other boats