Cape Donington marks the eastern side of the entrance to Boston Bay, within Lincoln National Park. The Marine Life Society describes generally sheltered shores with small granite and limestone caves and ledges in 2-4 m, with strapweed (Ecklonia radiata) and bushy brown algae, and depths to about 12 m. Boats launch from Kirton Point Caravan Park.

Offshore, Donnington Reef rises 3 m from the bottom about 550 m north-north-west of the cape, offering shallow granite reef diving with small ledges, overhangs and crevices. These reefs host a good cross-section of lower Eyre Peninsula temperate life: magpie perch, old wives, blue devils, wrasse, leatherjackets, sweep and western blue groper, with abalone, crabs, sea stars and nudibranchs in the crevices. The sheltered position makes Cape Donington a useful site when Thorny Passage and the outer islands are rough, and it pairs perfectly with the Degei wreck off nearby Donington Island.

The shallow shore ledges also suit snorkellers. It suits Open Water divers and snorkellers with a boat, and is a good introduction to the granite-reef diving of Lincoln National Park. The cape's lighthouse and the park's camping areas at nearby bays make it possible to combine diving with a few days in the park, and snorkellers in the party can explore the shallow ledges while divers do the deeper reef.

Currents are usually mild inside the bay entrance but can pick up off the tip of the cape on spring tides, so stay close to the reef and plan to return to the boat with gas in reserve. Visibility tends to be better here than inside Boston Bay proper.

Port Lincoln is about 650 km (7 hours) by road from Adelaide via Port Augusta and the Lincoln Highway, or a 45-50 minute flight (Rex/QantasLink). Launch at the Kirton Point Caravan Park ramp and run east across Boston Bay to Cape Donington (15-20 minutes). Cape Donington is also reachable by road within Lincoln National Park (park entry fee), where the lighthouse area gives views of the reefs.

Donnington Reef lies 550 m NNW of the cape.

Boston Bay and the waters around Port Lincoln are sheltered from Southern Ocean swell by Boston Island and the Lincoln National Park coast, so the town jetties can be dived in most weather; strong south-easterly and easterly winds are what chop them up. The islands of Thorny Passage and the lower Eyre coast are progressively more exposed to south-westerly swell and strong tidal streams, and need swell under about 1.5-2 m and light winds. Winter (May-August) brings frequent cold fronts with big south-westerly swell but also calm, clear spells; summer has more reliable weather but regular afternoon south-easterly sea breezes.

Water is cooler than the gulfs, around 13-15°C in winter and 17-20°C in summer.

Explore the small granite and limestone caves and ledges in 2-4 m along the shore, or dive Donnington Reef, working its ledges, overhangs and crevices at 3-10 m.

No regular operator; local divers and Port Lincoln dive shop customers with boats.