Australia
Best Time to Dive in the Neptune Islands
35.23°S 136.12°E
Go May to October for great white shark. 100% of days see seas over 1.5 m then, while the calmest water is December to April. Diving holds up from November to April.
- Best time
- May–Oct
- Water
- 15–20 °C
- Visibility
- 15–30 m
- Season runs
- Nov–Apr
- Dived from
- cage diving
- Tidal range
- 0.5–1.0 m
- Species logged
- 5
Worth knowing: 100% of days see seas over 1.5 m.
Where it is
111 km across · coastline from Natural Earth 10m
Diving in the Neptune Islands — monthly breakdown
A year of scuba diving conditions at a glance. Hover a month to isolate it.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Conditions | Poor | Poor | Poor | Poor | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Poor | Poor |
| Water temp (°C) | 19 | 20 | 20 | 18 | 18 | 17 | 16 | 15 | 15 | 16 | 16 | 18 |
| Visibility (m) | 20–30 | 20–30 | 20–30 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 20–30 | 20–30 | 20–30 | 20–30 |
| Marine life | Steady | Steady | Steady | Steady | Busy | Busy | Busy | Busy | Busy | Busy | Steady | Steady |
| Best time | Peak | Peak | Peak | Peak | Peak | Peak |
Excellent Good Moderate PoorPeak season May–Oct
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Neptune Islands diving season
May to October · Peak season
6 monthsJFMAMJJASOND
- Water temperature
- 15–18 °C
- Visibility
- 15–25 m
- Rain
- 11 days a month
Diving conditionsIt rains more.
November to April · Off season
6 monthsJFMAMJJASOND
- Water temperature
- 16–20 °C
- Visibility
- 20–30 m
- Rain
- 4 days a month
Diving conditionsIt rains less.
- Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
- Visibility is estimated from satellite chlorophyll-a.
Neptune Islands water temperature and weather
408 underwater observation records · 31 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Neptune Islands water temperature by month
The dashed line is the monthly average. Eight days in ten fall inside the band.
10th to 90th percentile rangemonthly mean
29
rough days a month
Seas top 1.5 m on 98% of days. Enough to cancel a day boat
8
blowy days a month
Gusts over 40 km/h, about where a day boat stays in port
7
wet days a month
1 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 3.2 m | 15% | 4 | 1 | 20 °C | 14.1 h |
| February | 3.8 m | 14% | 3 | 1 | 20 °C | 13.3 h |
| March | 3.7 m | 16% | 3 | 0 | 19 °C | 12.3 h |
| April | 3.8 m | 13% | 5 | 1 | 19 °C | 11.1 h |
| May | 4.7 m | 29% | 10 | 1 | 17 °C | 10.1 h |
| June | 5.4 m | 37% | 13 | 3 | 16 °C | 9.6 h |
| July | 5.1 m | 47% | 12 | 2 | 15 °C | 9.8 h |
| August | 4.8 m | 42% | 13 | 2 | 15 °C | 10.7 h |
| September | 4.7 m | 38% | 9 | 1 | 15 °C | 11.8 h |
| October | 4.1 m | 33% | 6 | 2 | 16 °C | 12.9 h |
| November | 3.9 m | 24% | 6 | 1 | 17 °C | 13.9 h |
| December | 3.5 m | 21% | 3 | 0 | 18 °C | 14.4 h |
Swell is the rough end of the month: nine days in ten come in under it. Sea temperature covers 10 years, waves 4.
Pick your week
48 weeks from the daily record. Darker is better, against this site's own year. Pick a month for the detail.
| Week 1 | January week 1: Poor | February week 1: Poor | March week 1: Poor | April week 1: Poor | May week 1: Good | June week 1: Good | July week 1: Excellent | August week 1: Excellent | September week 1: Excellent | October week 1: Excellent | November week 1: Moderate | December week 1: Poor |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Poor | February week 2: Poor | March week 2: Poor | April week 2: Poor | May week 2: Good | June week 2: Excellent | July week 2: Excellent | August week 2: Excellent | September week 2: Excellent | October week 2: Excellent | November week 2: Poor | December week 2: Poor |
| Week 3 | January week 3: Poor | February week 3: Poor | March week 3: Poor | April week 3: Poor | May week 3: Good | June week 3: Excellent | July week 3: Excellent | August week 3: Excellent | September week 3: Excellent | October week 3: Excellent | November week 3: Poor | December week 3: Poor |
| Week 4 | January week 4: Poor | February week 4: Poor | March week 4: Poor | April week 4: Poor | May week 4: Excellent | June week 4: Excellent | July week 4: Excellent | August week 4: Good | September week 4: Excellent | October week 4: Excellent | November week 4: Poor | December week 4: Poor |
Excellent Good Moderate PoorBest week to go: fourth of September
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 19 °C | 3.2 m | 33 km/h | 10% |
| Week 2 | Poor | 19 °C | 3.3 m | 33 km/h | 10% |
| Week 3 | Poor | 19 °C | 3.4 m | 32 km/h | 14% |
| Week 4 | Poor | 20 °C | 3.2 m | 33 km/h | 16% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 20 °C | 3.5 m | 34 km/h | 12% |
| Week 2 | Poor | 20 °C | 3.7 m | 33 km/h | 7% |
| Week 3 | Poor | 20 °C | 3.8 m | 31 km/h | 9% |
| Week 4 | Poor | 20 °C | 3.7 m | 31 km/h | 9% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 20 °C | 3.7 m | 32 km/h | 7% |
| Week 2 | Poor | 20 °C | 3.7 m | 32 km/h | 9% |
| Week 3 | Poor | 20 °C | 3.5 m | 31 km/h | 9% |
| Week 4 | Poor | 19 °C | 3.5 m | 30 km/h | 9% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 19 °C | 3.5 m | 29 km/h | 11% |
| Week 2 | Poor | 18 °C | 3.6 m | 29 km/h | 18% |
| Week 3 | Poor | 18 °C | 3.7 m | 29 km/h | 19% |
| Week 4 | Poor | 18 °C | 4.2 m | 30 km/h | 22% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 18 °C | 4.4 m | 33 km/h | 29% |
| Week 2 | Good | 18 °C | 4.4 m | 31 km/h | 27% |
| Week 3 | Good | 18 °C | 4.4 m | 31 km/h | 31% |
| Week 4 | Excellent | 17 °C | 5.5 m | 34 km/h | 38% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 17 °C | 5.6 m | 34 km/h | 38% |
| Week 2 | Excellent | 17 °C | 5.3 m | 35 km/h | 44% |
| Week 3 | Excellent | 17 °C | 5.5 m | 36 km/h | 48% |
| Week 4 | Excellent | 17 °C | 5.3 m | 36 km/h | 46% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 16 °C | 4.9 m | 36 km/h | 40% |
| Week 2 | Excellent | 16 °C | 5.1 m | 38 km/h | 41% |
| Week 3 | Excellent | 16 °C | 5.3 m | 41 km/h | 44% |
| Week 4 | Excellent | 16 °C | 5.0 m | 40 km/h | 39% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 15 °C | 4.6 m | 37 km/h | 41% |
| Week 2 | Excellent | 15 °C | 4.4 m | 38 km/h | 49% |
| Week 3 | Excellent | 15 °C | 4.5 m | 38 km/h | 41% |
| Week 4 | Good | 15 °C | 5.5 m | 37 km/h | 33% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 15 °C | 5.6 m | 38 km/h | 34% |
| Week 2 | Excellent | 15 °C | 4.8 m | 38 km/h | 31% |
| Week 3 | Excellent | 15 °C | 4.9 m | 37 km/h | 27% |
| Week 4 | Excellent | 15 °C | 4.7 m | 36 km/h | 24% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 15 °C | 4.4 m | 36 km/h | 22% |
| Week 2 | Excellent | 15 °C | 4.2 m | 35 km/h | 21% |
| Week 3 | Excellent | 16 °C | 3.8 m | 34 km/h | 20% |
| Week 4 | Excellent | 16 °C | 3.9 m | 34 km/h | 20% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 16 °C | 4.1 m | 34 km/h | 19% |
| Week 2 | Poor | 16 °C | 4.0 m | 34 km/h | 18% |
| Week 3 | Poor | 16 °C | 4.1 m | 32 km/h | 21% |
| Week 4 | Poor | 17 °C | 3.8 m | 32 km/h | 19% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 17 °C | 3.4 m | 32 km/h | 15% |
| Week 2 | Poor | 17 °C | 3.4 m | 34 km/h | 13% |
| Week 3 | Poor | 18 °C | 3.6 m | 34 km/h | 10% |
| Week 4 | Poor | 18 °C | 3.6 m | 33 km/h | 8% |
10 years of daily records, averaged into weeks.
Gear & storms
What to wear
Off the coldest water of each month, not the average — that is what the suit has to cope with.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Suit | January: 5 mm + | February: 5 mm + | March: 5 mm + | April: 5 mm + | May: 7 mm | June: 7 mm | July: 7 mm | August: 7 mm | September: 7 mm | October: 7 mm | November: 7 mm | December: 7 mm |
- Jan–Apr5 mm with hood and gloves
- May–Dec7 mm semi-dry
Swell through the year
The rough end of each month — nine days in ten come in under it.
Amber is over 1.5 m.
Tides
Tropical storms
No tropical storm has come within 250 km in 30 years of records. Swell and wind set the season, not cyclones.
- NOAASea surface temperature, from OISST and MUR
- ERA5Wind, waves, rain and air temperature, via Open-Meteo
- OBISMarine species records within 60 km
- IBTrACSTropical cyclone tracks, 1996 to 2025
Neptune Islands marine life — what you'll see diving
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Great white shark | All year | Likely | 211 | ||
| Common dolphin | Feb, Apr–May, Jul | Likely | 108 | ||
| Humpback whale | Jun–Jul | Hit-or-miss | 19 | ||
| Bottlenose dolphin | May | Hit-or-miss | 17 | ||
| Port Jackson shark | Oct–Dec | Hit-or-miss | 11 |
Peak Present
- Observed window
- Months with records. Peak is where most of them fall.
- Reliability
- Near-guaranteed in 60% of surveyed years or more
- Likely 30% to 60%
- Hit-or-miss under 30%
- Evidence
- Years it was seen, out of the years anyone surveyed.
- Records
- OBIS sightings within 60 km.
These are sightings people logged, not a full survey of the reef. A species missing from a month may just mean nobody recorded one.
Diving the Neptune Islands — common questions
- When is the best time to dive the Neptune Islands?
- Go May to October for great white shark. 100% of days see seas over 1.5 m then, while the calmest water is December to April. Diving holds up from November to April.
- When is the diving season at the Neptune Islands?
- Conditions are good November to April, but most divers come May to October for the marine life.
- How warm is the water at the Neptune Islands?
- Between 15 and 20 °C at the surface across the year, coldest in September and warmest in February. It runs cooler below the thermocline.
- What wetsuit do I need at the Neptune Islands?
- A 7 mm semi-dry covers the coldest water of the year. In the warmest months a 5 mm with hood and gloves is enough.
- What is the visibility like at the Neptune Islands?
- Roughly 15 to 30 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving the Neptune Islands?
- The most consistently recorded species are Great white shark (likely), Common dolphin (likely) and Humpback whale (hit-or-miss), from 408 records within 60 km.
- Does the Neptune Islands get tropical storms?
- No. None has passed within 250 km in 30 years of records.
- Is there current at the Neptune Islands?
- The tide rises and falls 1.0 m around the full and new moon, against 0.5 m in between. How much of that becomes current depends on the shape of the channel.
- When should I avoid the Neptune Islands?
- November–April are the weakest months for conditions.
- How do you dive the Neptune Islands?
- Mostly from a shark cage. Trips run through the season, Nov–Apr.