Philippines - El Nido: Nat Nat (Bacuit Archipelago)

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Part of the regional summaries: Philippines - Palawan and Philippines

Photo: Anderson Mayfield/Coral Reef Diagnostics

Country

Philippines

Survey date(s)

2017-01-24

Coordinates

11.1870, 119.3810

Approximate position: no GPS fix was logged for this dive.

Coral cover

14%^*

Claude computer vision (13 edited photos) · other methods below · median 10%

*Based on only 13 reef-habitat photos; this estimate is less certain.

Observations

None tagged; see Stressors below

Heat stress

Most recent heat load record

30.8°C 2.8°C-weeks

26 Oct 2026 · Bleaching Warning

5-year thermal stress load

5-year mean max. degree heating weeks (DHW)

3.2°C-weeksⁱ

2021–2025

NOAA Coral Reef Watch — Western Philippines virtual station

i 5-year mean max. DHW is the mean of the annual maximum DHWs over the five complete years named above, not conditions today.

More info

Western Philippines (NOAA CRW virtual station)

Photographs

19 shown on this page

Site summary

Read this summary in:

A murky, rough-conditions dive at Nat Nat turned up an Anacropora colony (Anderson's ID) and a large pale Plerogyra bubble coral, but the clearest condition note is a Seriatopora colony photographed and labeled dying. A blind Claude computer-vision point count puts coral cover around 14%.

Max. depth dived

24.1 m

Water temp. during survey

27.7°Cⁱⁱ

-1.5°C vs the 2017 mean sea temperature (29.2°C)

ii Logged water temperature of the dive (dive-computer average), 24 January 2017 (dive log); the dive computer's minimum was 27.2°C.

Bottom time

62 min

in at 09:54

Six independent survey stations shown with the program’s logo — click one to see how far it is from this site.

16 of the 19 photographs on this page are shown beside the text that discusses them under "Site description" below.

Photo credit & attribution

Site description

Setting

Conditions were poor and Anderson recorded them at the time — poor visibility (e.g., Image 7), dark water at depth (e.g., Image 13), and rough weather — which is worth carrying into any reading of these photographs.

General benthic features

The corals singled out in the log are the interesting part: Anacropora (Anderson's ID); a large pale Plerogyra bubble coral; and Seriatopora photographed twice, the second frame recorded as a dying colony, which stands as a clear condition observation at this site (e.g., Image 1, Image 5, Image 6, Image 11).

Around them are encrusting and massive colonies, foliose plates, and vivid red and pink encrusting sponges (e.g., Image 3, Image 7).

A distinctive lavender-gray cluster of tube sponges standing on open sand rounds out the benthos (e.g., Image 19).

Coral cover

Reference: Claude CV point count (this site's photos)
Coral cover: 14% — a blind Claude computer-vision point count of 13 of Anderson's edited photographs (20 points per photo; water, fish, and obstructions excluded). Other computer-vision methods are listed in the method table.

Stressors

One Seriatopora colony was photographed and recorded as dying (one frame); the cause is not stated.

Fish and other fauna

The fish and invertebrate list is varied for a murky dive: a school of big-eye barracuda with smaller barracuda alongside, a blue-spotted stingray on the sand, a lionfish, a bannerfish, and a very large host anemone with its anemonefish (e.g., Image 8, Image 10, Image 12, Image 13, Image 14, Image 18).

Two frames record chromodorid nudibranchs — blue and white bodies ruled with black lines, with yellow-orange rhinophores and gills (e.g., Image 15, Image 16); a third shows a different, pale white sea slug with black lines on orange substrate (e.g., Image 17).

Comparisons with other data

We found no other surveys at this site as of 2026. Within 5 km, six Reef Check stations recorded station-year means of 4.4–49% hard coral cover between 2013 and 2015; the nearest, Reef Check at Ipil MPA (Inside) Brgy. Buena Suerte, 1.26 km away, read 22–24% between 2013 and 2014.

Dive record

The first of three Bacuit Archipelago dives on 24 January 2017, in at 09:54 by bangka beneath the limestone karst, 62 minutes to a maximum of 24.1 m (mean 13.1 m) at 27.7°C average (dive-computer minimum 27.2°C); three of the 22 frames are topside.

CV model comparison

Mean 14%, median 10% across 13 photos.

More info

A few colony-focused photos raise the mean; the median is the typical photo. No computer-vision method yet estimates coral cover accurately on new images, so treat this as indicative rather than a measurement; it is revised as the methods improve.

Headline: Claude computer vision, a blind point count of this site's own photographs.

More info

DINOv3 and CoralSCOP were run on the site's photographs (see each row's n) and are listed for comparison. Coralscapes v2 is shown as its own row for comparison only: the author does not consider Coralscapes reliable for these photos, so it is low confidence and never enters any average or summary. No diver transect exists for this trip, so agreement between the rows is not accuracy, and no computer-vision method yet estimates coral cover accurately on new images; treat every row as indicative.

Method	Hard coral cover (%)	Photos (n) ± SE
In-house DINOv3	20.4*	n = 12 · SE 3.0
CoralSCOP edited	31.9*	n = 13 · SE 5.3
Claude (edited photos)	14.1*	n = 13 · SE 4.0
Coralscapes v2 (low confidence, never averaged)	20.7*

The two computer-vision methods disagree by 11.5 pp (20.4–31.9%) and read 6.3–17.8 pp above Claude's blind point count (14.1%); the headline is Claude's blind point count because no transect or manual count exists here.

*Based on only 12 reef-habitat photos; this estimate is less certain. (In-house DINOv3, Coralscapes v2 (low confidence, never averaged))

*Based on only 13 reef-habitat photos; this estimate is less certain. (CoralSCOP edited, Claude (edited photos))

See a more detailed, stand-alone version of this table.

Independent surveys nearby

Within 5 km, 6 independent survey stations recorded hard coral cover in 13 surveys between 2013 and 2015. Of the 6 stations surveyed in more than one year, 2 declined (by 4.0–16 points), 3 increased (by 2.0–13 points), and 1 changed by less than 1 point between their first and latest surveys. The longest record, Maitre MPA (Inside) (Reef Check, 4.86 km away), went from 28% in 2013 to 24% in 2015. The most recent nearby survey is from 2015, so these values predate recent heat stress. This site's own estimate (14%) sits within the range of these station-year means up to 2 km away (4.4–49%); the methods differ, so the comparison is context, not a like-for-like test.

Collected by other programs using different methods (Reef Check uses point-intercept transects), so these are context for the figures above, not a like-for-like comparison. Where a station was surveyed more than once, the cell shows either the range of its values or, as a single value, the mean of surveys made in one year. Station names are not dive-site names.

Independent survey data near this site
Agency	Site / location	Date	Hard coral cover (%)	Distance
Reef Check	Ipil MPA (Inside) Brgy. Buena Suerte	2013–2014	22–24% (2 surveys)	1.26 km
Reef Check	Caalan MPA B	2013–2014	29–45% (2 surveys)	1.27 km
Reef Check	7th Comando Outside	2013–2014	4.4–7.5% (2 surveys)	1.65 km
Reef Check	Caalan MPA A	2013–2014	36–49% (2 surveys)	1.79 km
Reef Check	Bukal	2013–2014	34% (2 surveys)	2.60 km
Reef Check	Maitre MPA (Inside)	2013–2015	24–33% (3 surveys)	4.86 km

Data & links

All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics and the organizations named in the data sources above.