The Oceans Surrounding Phang Nga Bay, Thailand
- The Persaud Foundation
- Apr 20
- 6 min read
Phang Nga Bay is a bay on the southern coast of Thailand, between the mainland & Phuket Island. It is well known for its small islands dotted around the bay, limestone formations, underwater caves, & mangrove forests.
Many divers flock to the area each year to photograph marine animals, swim in the bay, & take in the surreal beauty around them. There are many areas for swimming, kayaking, snorkelling, & picnicking on the islands in the bay & on the mainland coastline bordering the bay. It is common for tourists to travel between Phuket, & the Phang Nga, as the drive is approximately 1 hour & 54 minutes under optimal circumstances.
Many tourists travelling the coast of Thailand will pass through the area for a day trip, to enjoy the beauty of the area. The entire bay is protected as a marine protected area as part of Ao Phang Nga National Park. In addition to its beautiful landscape, the island is extremely biodiverse.
The bay is filled with many beautiful ecosystems, ranging from mangrove forests to coral reefs. One of the popular creatures of the area, is known as the Giant Oceanic Manta Ray. We published an article about this species on the 10th of this month, & it can be found by typing “Manta Ray” into the search function of our website.
In this article, we will be discussing the salinity, tides, temperatures, marine geography, & depth of the oceans surrounding Phang Nga Bay, the most prominent marine ecosystems of Phang Nga Bay, the marine flora & fauna of Phang Nga Bay, & finally how ocean acidification & rising oceanic temperatures are affecting Phang Nga Bay. With that being said, let us delve into this gorgeous Thai paradise!
The Salinity, Tides, Temperatures, Marine Geography, & Depth of The Oceans Surrounding Phang Nga Bay
Unfortunately, the salinity of Phang Nga Bay is unmeasured. The salinity of the Indian Ocean where the bay is located ranges from 32 parts per thousand, to 37 parts per thousand. Salinity is measured in 1000-gram increments of water, & for every 1000 grams of water, a certain amount is salt. This measurement is called parts per thousand, or practical salinity units. There are not many recorded brine pools inside the bay, & there are very few salt deposits.
The tidal charts for Phang Nga Bay can be found on many websites, including https://www.tideschart.com, https://nashaplaneta.net, & https://nashaplaneta.net. The tides of the bay usually do not rise above 3.54 meters (11.61417 feet), & sit below 0.27 meters (0.8858268 feet).
The oceanic temperatures can be found on similar websites, such as: https://www.seatemperature.org, & https://www.tideschart.com. Using the data given by these sources, the average yearly temperature is approximately 29.316666666667° Celsius (84.7700000000005929° Fahrenheit). At this temperature, no wetsuit is needed to comfortably swim. There is very little riptide in the bay, & few dangerous currents that pose a threat to humans. Although there are rip currents, they are very minor. The bay is safe for swimmers, & is not very polluted. There are very few environmental hazards in the bay that would limit swimming.
Both snorkelling & scuba diving are incredibly popular in the bay. Kayaking is also fairly popular, with kayaking tours being particularly popular in the areas with limestone caves.
The bay has a fair amount of coral, & is relatively shallow. The deepest part of the bay is approximately 40 meters (131.234 feet) deep. Most areas consist of a mud or sand sea bottom. The entire bay is protected as a marine protected area, as a part of the Ao Phang Nga National Park.
The Most Prominent Marine Ecosystems of Phang Nga Bay
Ecosystem Type No. 1: Mangrove Forest
Coastal mangrove forests are a particular kind of forest, that adorn the shoreline of the bay. A mangrove forest is a type of forest that grows in saltwater or brackish environments, in the intertidal zone. They often have exposed tree roots, known as aerial roots. These forests are incredibly important to biodiversity, for terrestrial, oceanic, & avian creatures. The forest provides shelter, food, & a spawning ground for many different species.
Additionally, they provide a buffer between the land & the ocean for storms, such that if a hurricane or storm were to occur, the mangrove forest could absorb some of the damage. The mangroves also protect against flooding from storm surges. Many trails can be found leading through these forests, which attract many ecotourists.
The two major species of Mangrove Tree found in this area are Rhizophora apiculata (Tall-Stilt Mangrove), & Bruguiera gymnorrhiza (Large-Leafed Orange Mangrove).
Ecosystem Type No. 2: Fringing Coral Reefs
Coral reefs are massive structures of coral polyps, typically located along the ocean floor. These coral reefs act as a breeding ground, hunting ground, spawning ground, & shelter. There are various kinds of coral reefs, the most important of which are atoll, barrier, & fringing. The coral reefs in the bay are of the fringing kind, meaning that they grow directly against the shoreline, without a significant water barrier.
Unfortunately, there is no report or compendium of marine species that inhabit the coral reefs of Phang Nga Bay.
Ecosystem Type No. 3: Sunken Caves
Sunken Caves are common in Phang Nga Bay. These caves are located underwater, & extend into cave systems occasionally. These caves largely serve as shelter for marine animals, & the majority of them are located on the western side of the bay.
The Documented Marine Flora of Phang Nga Bay
Unfortunately, it is not clear what species of seagrass or algae inhabit the bay. For this reason, we are going to instead dedicate this section to the mangrove trees of the area.
Mangrove Tree No. 1: Rhizophora Apiculata (Tall-Stilt Mangrove)
Rhizophora Apiculata is a species of Mangrove Tree native to the Indo-Pacific, & Australia. The tree has a light to dark greyish bark, with beautiful 4-petalled yellow flowers. The shape of the tree is conical. Individual trees in this species range from 16 meters to 30 meters in height. It is not endangered internationally, it is endangered in specific countries.
Mangrove Tree 2: Bruguiera Gymnorrhiza (Large-Leafed Orange Mangrove)
The Large Leafed Orange Mangrove is a species of mangrove tree native to the Indo-Pacific, Indian Subcontinent, & Polynesia. The tree is very recognizable for its large leaves, & its dark red to black bark. It produces large Red or Orange flowers, with yellow centers. Individual Trees themselves are between 16 & 20 meters tall.
The Documented Marine Fauna of Phang Nga Bay
Though Phang Nga Bay is extremely biodiverse, there have been no animal surveys of the bay yet, meaning we do not have a comprehensive understanding of the marine animals that inhabit the bay. Species such as Mobula birostris (Giant Oceanic Manta Ray), Rhincodon typus (Whale Shark), Eretmochelys imbricata (Hawksbill Turtle), Chelonia mydas (Green Sea Turtle), & Lepidochelys olivacea (Olive Ridley Sea Turtle), are all commonly found in the bay.
In addition to being biodiverse, the bay is also a haven for an endangered species of porpoise. The bay is home to the Black Finless Porpoise, an endangered species of Porpoise found in the Indian & Pacific Oceans.
How Ocean Acidification, & Rising Oceanic Temperatures Are Affecting Phang Nga Bay
Ocean acidification is caused by increased levels of carbon dioxide in the atmosphere. Atmospheric carbon dioxide levels have increased, largely because of human-caused burning of fossil fuels, & deforestation, for the past 150 years. When carbon dioxide contacts seawater, it forms carbonic acid. Carbonic acid gives off positive H+ ions, which causes increased oceanic H+ concentrations & decreased oceanic pH. When the ocean has decreased pH, it effectively acidifies. When this happens, it causes conditions that will eat at the shells of bivalves, stress out & eventually bleach coral, & utterly destroy seagrass patches.
As of 2026, it is not clear if ocean acidification is affecting the coral reefs of Thailand. More long-term monitoring data is needed to make a conclusive determination, which is currently not available. If current trends continue, then ocean acidification will likely devastate the coral reefs of Phang Nga Bay.
Directories / Credits
Citation No. 1: “Ao Phang-Nga National Park - Thailand's most famous marine protected area”, Written by Unknown, & Published at an Unknown Date. Published by the Secretariat of the Convention on Biological Diversity. Retrieval Date: April 30th, 2024.
Citation No. 2: “Mangrove forest in Phang Nga Bay, Andaman Sea, Thailand”, Written by Unknown & Published at an Unknown Date. Published by Peapix. Retrieval Date: April 30th, 2024.
Citation No. 3: “Rhizophora apiculata Blume”, Written by Unknown, & Published at an Unknown Date. Published by Flora & Fauna Web. Retrieval Date: April 30th, 2024.
Citation No. 4: “Large-Leafed Orange Mangrove”, Written by Unknown, & Published at an Unknown Date. Published by Mangroves. Retrieval Date: April 30th, 2024.
Citation No. 5: “Bruguiera Gymnorrhiza”, Written by Unknown, & Published at an Unknown Date. Published by the Flora & Fauna Web. Retrieval Date: April 30th, 2024.
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