Caribbean Reef Octopus (Octopus briareus)
A dive briefing · Grand Cayman, Cayman Islands

Bonnie's Arch

Dive site at a Cayman Islands Department of Environment public mooring off Grand Cayman. Here's what has been recorded at this site month by month, how the region’s reefs have weathered ocean heat, and how to prepare.

Grand Caymanreef
At this sitegeotagged 557 m from the site coordinates Caribbean Reef Octopus (Octopus briareus) · Dan Schofield · CC BY 4.0 · iNaturalist
Painted Elysia (Thuridilla picta)
Chapter I · Arrival

Bonnie's Arch: dive site at a Cayman Islands Department of Environment public mooring off Grand Cayman.

19.370° N81.419° W · Cayman Islands DoE public moorings 2023
2,511open records · GBIF
236+species recorded
At this sitegeotagged 537 m from the site coordinates Painted Elysia (Thuridilla picta) · Dan Schofield · CC BY 4.0 · iNaturalist
II

Entry

Painted Elysia (Thuridilla picta)

Shore and boat entries vary by site. We list only rules we can cite from official sources; entry points, depths and currents will be added once we can verify them.

To verifyDepth range, entry points and current notes. We publish them only with a citation. The coordinates mark the site in general, not a mooring or entry point.
Local rules (cited)
  • The DoE has installed public moorings to protect reefs from anchor damage. Use a mooring instead of anchoring whenever possible; it is an offence to damage coral anywhere in Cayman waters. Cayman Islands DoE · Public Moorings
  • The maximum stay on a public mooring is 3 hours. Do not use moorings in winds of 25 knots or more. Cayman Islands DoE · Public Moorings
  • Marine Park zones carry their own rules (for example, no taking of marine life in Marine Reserve zones and no SCUBA diving in No Diving zones without permission). Check the zone with the DoE app or brochures. Cayman Islands DoE · Marine Parks
  • Wildlife Interaction Zones are the only places in the Cayman Islands where you may legally feed or interact with marine life. Cayman Islands DoE · Marine Manners

At this sitegeotagged 537 m from the site coordinates Painted Elysia (Thuridilla picta) · Dan Schofield · CC BY 4.0 · iNaturalist

▶
Captain's footage: Bonnie's Arch
[video slot · coming soon]

The surface noise falls away.

Reds go first. The world turns blue-green.

Then Bonnie's Arch rises to meet you.

Caribbean Reef Octopus (Octopus briareus)
IV

What lives here, by month

Pick a month. These are the species most often recorded within about a kilometre in that month, from open survey records.

Oct
October · 164 qualifying records
Life calendar · records per month for this site's most-recorded species (blank means not in that month's top list)
SpeciesJanFebMarAprMayJunJulAugSepOctNovDec
Flamingo tongue snail
Lined sea hare
Tritonicula hamnerorum
Lettuce slug
Bermuda shrimp
Banded-antennae squat shrimp
Stoplight Parrotfish
Yellow stingray
Sailfin Blenny
French angelfish
Elysia cornigera
Banded clinging crab

Most-recorded species, all months

  1. Flamingo tongue snail (25)
  2. Lined sea hare (17)
  3. Tritonicula hamnerorum (15)
  4. Lettuce slug (14)
  5. Bermuda shrimp (11)
  6. Banded-antennae squat shrimp (10)
  7. Stoplight Parrotfish (10)
  8. Sailfin Blenny (9)
  9. French angelfish (9)
  10. Yellow stingray (9)
  11. Elysia cornigera (9)
  12. Banded clinging crab (8)
  13. Foureye butterflyfish (8)
  14. Bar jack (8)
  15. Ocean Triggerfish (8)
  16. Longspine squirrelfish (8)
  17. Queen Angelfish (8)
  18. Spotted Spiny Lobster (7)
  19. Bluehead Wrasse (7)
  20. Mutton snapper (7)

GBIF.org (2026-10-14), occurrence records within ~1 km, licensed CC0 or CC BY 4.0 only. Birds and land animals are excluded. Counts reflect survey effort, not abundance. 2,511 qualifying records. See them on GBIF. Common names: Wikidata (CC0) / GBIF. Species photos: Wikimedia Commons, credited with each species.

V

Forty-one summers of heat

Each stripe is one year since 1985, colored by its peak heat stress across NOAA's “Cayman Islands” region. These are NOAA Coral Reef Watch satellite figures for the whole region, not for this one site.

19852026
Reef health report · Cayman Islands

Heat stress, measured from orbit.

Degree Heating Weeks · 2026-10-1311.9°C-weeks · NOAA status: Bleaching Watch

NOAA CRW virtual station “Cayman Islands”. NOAA's alert thresholds are 4 °C-weeks (Alert Level 1) and 8 °C-weeks (Alert Level 2). Station page · Method. Credit: NOAA Coral Reef Watch.

Peak per year · dashed lines at 4, 8 and 16 °C-weeks
The past twelve months
VI

Conditions

Average sea temperature through the year. Check the live readings before you go.

Average sea surface temperature by month: NOAA CRW “Cayman Islands” station climatology (monthly means).

Buoy readings are measurements; forecasts are models. Use them for planning only, and assess conditions on site. Depth and visibility data aren't listed until we can cite a source.

VII

Plan & prepare

  1. Read the official marine forecast the night before.Offshore, wind and sea state decide the day.
  2. Check the cited local rules above and pay any park fee before you dive.[Placeholder: verified operator list to come]
  3. Study this month's species above.You'll recognise more when you know the names.
  4. Hands off, fins up, buoyancy dialled. Log what you see.Your sightings can become tomorrow's open data.

Credits

Coordinates
Cayman Islands DoE public moorings 2023 (WEST), mooring "Bonnie's Arch" · source · government publication. Cayman Islands Department of Environment, Public Moorings (updated January 2023). Each site uses the coordinates of the named public mooring.
Species records
GBIF.org, CC0 & CC BY 4.0 records. By license: CC_BY_4_0: 2,460, CC0_1_0: 51
Dataset
EOD – eBird Observation Dataset · doi:10.15468/aomfnb (1,658 records) · GBIF
Dataset
iNaturalist Research-grade Observations · doi:10.15468/ab3s5x (833 records) · GBIF
Dataset
Birda - Global Observation Dataset · doi:10.15468/6kud7x (18 records) · GBIF
Dataset
CAS Invertebrate Zoology (IZ) · doi:10.15468/tiac99 (2 records) · GBIF
Query
https://api.gbif.org/v1/occurrence/search?decimalLatitude=19.36038,19.380380000000002&decimalLongitude=-81.4295,-81.4095&license=CC0_1_0&license=CC_BY_4_0&taxonKey=44&taxonKey=206&taxonKey=229&taxonKey=136&taxonKey=225&occurrenceStatus=PRESENT&limit=0
Heat stress & SST
NOAA Coral Reef Watch, 5 km Regional Virtual Station “Cayman Islands”
Hero photo
At this sitegeotagged 557 m from the site coordinates Caribbean Reef Octopus (Octopus briareus) · Dan Schofield · CC BY 4.0 · iNaturalist
Arrival photo
At this sitegeotagged 537 m from the site coordinates Painted Elysia (Thuridilla picta) · Dan Schofield · CC BY 4.0 · iNaturalist
Gallery
5 photos, credited under each image
Species photos
Wikimedia Commons, credited with each species. Full list: Data & sources