Indonesia
Best Time to Dive in Derawan / Sangalaki
2.10°N 118.40°E
Dive it April to August, when the downpours ease — 7 days a month of heavy rain instead of 9. Too few records to show a wildlife season, so the weather picks the month. The full season runs March to September.
- Best time
- Apr–Aug
- Water
- 29–30 °C
- Visibility
- 10–25 m
- Season runs
- Mar–Sep
- Dived from
- day boat
- Tidal range
- 0.9–2.4 m
- Species logged
- 3
Worth knowing: 7 days a month of heavy rain.
Where it is
111 km across · coastline from Natural Earth 10m
Diving in Derawan / Sangalaki — 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 | Moderate | Good | Good | Good | Excellent | Excellent | Excellent | Excellent | Moderate | Poor | Poor |
| Water temp (°C) | 29 | 29 | 29 | 30 | 30 | 30 | 30 | 29 | 30 | 30 | 30 | 29 |
| Visibility (m) | 10–20 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 |
| Marine life | Steady | Steady | Busy | Steady | Peak | Peak | Peak | Peak | Peak | Busy | Steady | Steady |
| Best time | Peak | Peak | Peak | Peak | Peak |
Excellent Good Moderate PoorPeak season Apr–Aug
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Derawan / Sangalaki diving season
February · Shoulder season
1 monthJFMAMJJASOND
- Water temperature
- 29–29 °C
- Visibility
- 15–25 m
- Rain
- 25 days a month
Diving conditionsThe wind is up.
March to September · Peak season
7 monthsJFMAMJJASOND
- Water temperature
- 29–30 °C
- Visibility
- 15–25 m
- Rain
- 24 days a month
Diving conditionsSeas are usually flat. This is the wet season topside.
Marine lifeWhale shark (likely), Reef manta (likely) peak at Derawan / Sangalaki in these months.
October · Shoulder season
1 monthJFMAMJJASOND
- Water temperature
- 30–30 °C
- Visibility
- 15–25 m
- Rain
- 25 days a month
Diving conditionsThe wind is up.
November to January · Off season
3 monthsJFMAMJJASOND
- Water temperature
- 29–30 °C
- Visibility
- 15–25 m
- Rain
- 28 days a month
Diving conditionsThe wind eases.
- Spring tides run 2.4 m against 0.9 m on neaps, so currents build around the full and new moon.
- Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
- Visibility is estimated from satellite chlorophyll-a.
Derawan / Sangalaki water temperature and weather
100 underwater observation records · 16 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Derawan / Sangalaki 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
Rarely
rough enough to cancel
Seas top 1.5 m on under 1% of days. Enough to cancel a day boat
0
blowy days a month
Gusts over 40 km/h, about where a day boat stays in port
25
wet days a month
8 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 0.6 m | 0% | 29 | 12 | 28 °C | 11.9 h |
| February | 0.7 m | 0% | 25 | 8 | 28 °C | 11.9 h |
| March | 0.6 m | 0% | 26 | 8 | 28 °C | 12.0 h |
| April | 0.4 m | 0% | 23 | 7 | 29 °C | 12.0 h |
| May | 0.3 m | 0% | 27 | 9 | 29 °C | 12.1 h |
| June | 0.4 m | 0% | 25 | 7 | 29 °C | 12.1 h |
| July | 0.6 m | 0% | 21 | 6 | 29 °C | 12.1 h |
| August | 0.4 m | 0% | 21 | 6 | 29 °C | 12.1 h |
| September | 0.5 m | 0% | 22 | 7 | 29 °C | 12.0 h |
| October | 0.5 m | 0% | 25 | 9 | 29 °C | 12.0 h |
| November | 0.4 m | 0% | 26 | 9 | 29 °C | 11.9 h |
| December | 0.3 m | 0% | 28 | 11 | 29 °C | 11.9 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: Good | March week 1: Moderate | April week 1: Excellent | May week 1: Good | June week 1: Excellent | July week 1: Excellent | August week 1: Excellent | September week 1: Excellent | October week 1: Good | November week 1: Poor | December week 1: Poor |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Poor | February week 2: Moderate | March week 2: Moderate | April week 2: Excellent | May week 2: Good | June week 2: Good | July week 2: Excellent | August week 2: Excellent | September week 2: Good | October week 2: Good | November week 2: Poor | December week 2: Poor |
| Week 3 | January week 3: Poor | February week 3: Poor | March week 3: Good | April week 3: Excellent | May week 3: Good | June week 3: Excellent | July week 3: Good | August week 3: Excellent | September week 3: Good | October week 3: Poor | November week 3: Moderate | December week 3: Poor |
| Week 4 | January week 4: Poor | February week 4: Moderate | March week 4: Excellent | April week 4: Excellent | May week 4: Moderate | June week 4: Excellent | July week 4: Good | August week 4: Excellent | September week 4: Excellent | October week 4: Poor | November week 4: Moderate | December week 4: Poor |
Excellent Good Moderate PoorBest week to go: first of July
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 0.4 m | 19 km/h | 94% |
| Week 2 | Poor | 29 °C | 0.6 m | 19 km/h | 95% |
| Week 3 | Poor | 29 °C | 0.6 m | 19 km/h | 94% |
| Week 4 | Poor | 29 °C | 0.7 m | 21 km/h | 89% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 29 °C | 0.7 m | 21 km/h | 87% |
| Week 2 | Moderate | 29 °C | 0.6 m | 22 km/h | 85% |
| Week 3 | Poor | 29 °C | 0.6 m | 22 km/h | 83% |
| Week 4 | Moderate | 29 °C | 0.7 m | 22 km/h | 85% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 29 °C | 0.7 m | 21 km/h | 85% |
| Week 2 | Moderate | 29 °C | 0.6 m | 20 km/h | 80% |
| Week 3 | Good | 29 °C | 0.6 m | 20 km/h | 84% |
| Week 4 | Excellent | 29 °C | 0.5 m | 19 km/h | 90% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 30 °C | 0.4 m | 19 km/h | 81% |
| Week 2 | Excellent | 30 °C | 0.5 m | 18 km/h | 72% |
| Week 3 | Excellent | 30 °C | 0.4 m | 18 km/h | 71% |
| Week 4 | Excellent | 30 °C | 0.3 m | 16 km/h | 82% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 30 °C | 0.3 m | 16 km/h | 89% |
| Week 2 | Good | 30 °C | 0.3 m | 16 km/h | 86% |
| Week 3 | Good | 30 °C | 0.3 m | 16 km/h | 89% |
| Week 4 | Moderate | 30 °C | 0.4 m | 17 km/h | 87% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 30 °C | 0.3 m | 17 km/h | 83% |
| Week 2 | Good | 30 °C | 0.4 m | 17 km/h | 84% |
| Week 3 | Excellent | 30 °C | 0.4 m | 17 km/h | 87% |
| Week 4 | Excellent | 30 °C | 0.4 m | 17 km/h | 85% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 30 °C | 0.4 m | 18 km/h | 78% |
| Week 2 | Excellent | 29 °C | 0.5 m | 19 km/h | 71% |
| Week 3 | Good | 29 °C | 0.6 m | 22 km/h | 63% |
| Week 4 | Good | 29 °C | 0.6 m | 22 km/h | 60% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 29 °C | 0.5 m | 21 km/h | 59% |
| Week 2 | Excellent | 29 °C | 0.4 m | 20 km/h | 63% |
| Week 3 | Excellent | 29 °C | 0.4 m | 19 km/h | 67% |
| Week 4 | Excellent | 29 °C | 0.5 m | 19 km/h | 73% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 30 °C | 0.6 m | 19 km/h | 78% |
| Week 2 | Good | 30 °C | 0.6 m | 19 km/h | 75% |
| Week 3 | Good | 30 °C | 0.6 m | 19 km/h | 67% |
| Week 4 | Excellent | 30 °C | 0.4 m | 18 km/h | 74% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 30 °C | 0.4 m | 16 km/h | 83% |
| Week 2 | Good | 30 °C | 0.4 m | 16 km/h | 83% |
| Week 3 | Poor | 30 °C | 0.5 m | 17 km/h | 82% |
| Week 4 | Poor | 30 °C | 0.6 m | 17 km/h | 79% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 30 °C | 0.6 m | 17 km/h | 80% |
| Week 2 | Poor | 30 °C | 0.4 m | 17 km/h | 85% |
| Week 3 | Moderate | 30 °C | 0.4 m | 17 km/h | 90% |
| Week 4 | Moderate | 30 °C | 0.4 m | 16 km/h | 94% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 30 °C | 0.3 m | 17 km/h | 95% |
| Week 2 | Poor | 29 °C | 0.3 m | 18 km/h | 89% |
| Week 3 | Poor | 29 °C | 0.4 m | 19 km/h | 86% |
| Week 4 | Poor | 29 °C | 0.4 m | 19 km/h | 91% |
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: skin | February: skin | March: skin | April: skin | May: skin | June: skin | July: skin | August: skin | September: skin | October: skin | November: skin | December: skin |
One suit covers the whole year: a skin or 3 mm shorty.
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
Derawan / Sangalaki marine life — what you'll see diving
Only 100 records have been logged within 60 km. A thin record is not an empty reef.
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Green turtle | All year | Near-guaranteed | 32 | ||
| Whale shark | Jul–Aug | Likely | 11 | ||
| Reef manta | May–Jun, Sep | Likely | 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 Derawan / Sangalaki — common questions
- When is the best time to dive Derawan / Sangalaki?
- Dive it April to August, when the downpours ease — 7 days a month of heavy rain instead of 9. Too few records to show a wildlife season, so the weather picks the month. The full season runs March to September.
- When is the diving season in Derawan / Sangalaki?
- The diving season in Derawan / Sangalaki runs March to September, and it is at its best April to August.
- Is the diving in Derawan / Sangalaki good for beginners?
- Yes. It suits Open Water divers, so it works for a first trip after certification.
- How warm is the water in Derawan / Sangalaki?
- Between 29 and 30 °C at the surface across the year, coldest in February and warmest in May. It runs cooler below the thermocline.
- What wetsuit do I need in Derawan / Sangalaki?
- A skin or 3 mm shorty covers the coldest water of the year. The same suit works all year.
- What is the visibility like in Derawan / Sangalaki?
- Roughly 10 to 25 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving Derawan / Sangalaki?
- The most consistently recorded species are Green turtle (near-guaranteed), Whale shark (likely) and Reef manta (likely), from 100 records within 60 km.
- Does Derawan / Sangalaki get tropical storms?
- No. None has passed within 250 km in 30 years of records.
- Is there current in Derawan / Sangalaki?
- The tide rises and falls 2.4 m around the full and new moon, against 0.9 m in between. How much of that becomes current depends on the shape of the channel.
- When should I avoid Derawan / Sangalaki?
- December–January are the weakest months for conditions.
- How do you dive Derawan / Sangalaki?
- Mostly from day boats. Trips run through the season, Mar–Sep.