Meet the site
Bessieres (spelt Bessiers by the Marine Life Network) Island has coral ridges and bommies at 12–19 m with schooling fish, giant potato cod, moray eels and turtles that approach divers.
About the Mackerel Islands: the group of ten low islands off Onslow, including Thevenard and Direction islands, sits just north of the Ningaloo Coast and Exmouth Gulf. The Marine Life Network documents a dozen dive sites within easy reach of Thevenard, from shallow coral heads to ledges, caves and canyons at up to 20 m, and the resort notes whales, dolphins, groper, reef sharks, stingrays, wobbegongs, turtles and thick schools of trevally, snapper, fusiliers and batfish. With no resident operator and few visiting divers, the reefs are among the least dived in the region — ideal for self-sufficient divers with their own boat.
Planning notes: Advanced Open Water certification is recommended and the site is rated intermediate. Expect to spend most of the dive around 15 m, with a maximum of about 19 m. Access is by boat only, and site selection depends on wind, swell and tide on the day. Best season: April–October. Traffic: rarely dived (private boat/club only).
What you might see
Giant potato cod, moray eels, turtles, schooling fish
Location
Island in the Onslow/Mackerel group with coral ridges and bommies at 12–19 m, home to giant potato cod.
Facilities nearby
Mackerel Islands resort on Thevenard Island: accommodation, snorkel gear hire, boat hire. No air fills – bring filled cylinders or arrange via Karratha.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
marinelife.org.aumackerelislands.com.auRecord updated 26 Sept 2026. Source claims are being reviewed.