When To Go · Destination Guide
Wild kelp forests and predator free islands off the Coromandel coast
When to go
Mercury Bay and the Mercs are a genuinely year round diving area, but conditions feel very different between seasons.
Best overall window
Warmest water near 20°C, long daylight, frequent light winds and settled high pressure. Accommodation and charters are busiest from late December to early February.
Outside that window
Coolest water and air, more frequent swell and strong wind events, but also occasional crystal clear, calm days under winter high pressure systems.
Start with the overall answer, then switch only when scuba, freedive, snorkel, or topside timing changes the trip in a meaningful way.
The overall row stays visible so you can compare it against the currently selected scope.
| Scope | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall | Overall - Jan: Best | Overall - Feb: Best | Overall - Mar: Best | Overall - Apr: Best | Overall - May: Good | Overall - Jun: Tradeoffs | Overall - Jul: Tradeoffs | Overall - Aug: Tradeoffs | Overall - Sep: Tradeoffs | Overall - Oct: Tradeoffs | Overall - Nov: Good | Overall - Dec: Good |
These do not replace the overall planner. Use them only if a specific animal or event is driving your trip dates.
Schooling pelagics and kingfish
Best for Scuba, Freedive
Dec to Mar
Summer brings larger schools of kahawai, trevally and kingfish to current swept Mercs points and pinnacles such as Never Fail Rock, where birds work bait and pelagics hunt through the water column.
Winter whales and dolphins
Best for Scuba, Snorkel, Topside
Jun to Sep
Humpback and other migratory whales transit the Hauraki Gulf and wider Coromandel waters in winter, and pods of common and bottlenose dolphins can show up in any season.
Seabird breeding on pest free islands
Best for Topside, Scuba
Oct to Jan
Pest free Mercury Islands support dense colonies of seabirds, including petrels and terns, particularly on Middle and Green Islands that have never had mammalian pests.
Dark skies and bioluminescence
Best for Snorkel, Topside
May to Aug
Overnight boat trips and, where permitted, stays at Ahuahu can coincide with exceptionally dark skies and occasional bioluminescent plankton in sheltered bays, making for memorable night sky photography and night snorkelling from the boat on calm, safe evenings.
Built from climate references, access rules, and destination operators. Wildlife timing and route flexibility can shift year to year.