Where to dive with dugongs and manatees

What they are

The dugong can grow to about three metres and weigh up to 400 kilograms, according to the Great Barrier Reef Marine Park Authority. It is the only marine mammal in Australia that lives mainly on plants, grazing on seagrass meadows in sheltered coastal water, and it can live up to 70 years.¹

The West Indian manatee is larger: the US Fish and Wildlife Service says adults are typically 9 to 10 feet long and around 1,000 pounds, with some reaching more than 13 feet and 3,500 pounds. Manatees spend up to 8 hours a day eating seagrass or other plants.²

Where and when divers see them

Dugongs favour warm, shallow inshore water and reef seagrass beds, usually at 1 to 40 metres. The Great Barrier Reef region supports globally significant populations, and a draft global assessment of dugong status prepared for the Convention on Migratory Species lists 34 countries and territories with resident populations.^1,3,4

Manatees use shallow areas near the shore with seagrass and other underwater plants. Florida manatees cannot tolerate water below 68°F for long, so in winter many gather at warm natural springs, power plant outfalls and thermal basins. The West Indian manatee also occurs across Central and South America.^2,5

Conservation status

The dugong and the West Indian manatee are both listed as Vulnerable on the IUCN Red List. SeaLifeBase, which reproduces the Red List entries, gives the dugong assessment date as 12 July 2015 and the West Indian manatee's as 4 September 2023. Some dugong populations are more threatened: according to a draft global dugong assessment prepared for CMS, the IUCN listed the East African coastal subpopulation as Critically Endangered in 2022.^3,4,6

In the United States, manatees are federally protected under the Endangered Species Act and the Marine Mammal Protection Act, and in Florida it is unlawful to annoy, molest, harass or disturb any manatee.^2,7

How to behave around them

Florida's Fish and Wildlife Conservation Commission advises that, where in-water activities are allowed, people use snorkel gear and float at the surface to observe manatees passively, keep their distance and give manatees space to move. Dugong guidelines developed in Vanuatu by the Vanuatu Environmental Science Society, under a project supported by the CMS Dugong Secretariat, ask swimmers not to swim towards a dugong, but to stay where they are and let it come to them if it wants to.^7,8

• Florida (FWC): do not touch, poke, prod or feed manatees. Vanuatu dugong guidelines: never try to touch a dugong on the head, and do not feed dugongs.^7,8
• Florida (FWC): if a manatee avoids you, do not chase it for a closer view.⁷
• Florida (FWC): do not single out a manatee or separate a cow and her calf. Vanuatu dugong guidelines: keep at least 5 metres from a mother and calf.^7,8
• Vanuatu dugong guidelines: no more than 5 people within 10 metres of a dugong, and when a dugong has approached you, stay at least 2 metres from its tail.⁸
• Florida (FWC): avoid excessive noise and splashing near manatees. Vanuatu dugong guidelines: if a dugong shows signs of distress, such as repeatedly swimming away, stop and move at least 50 metres away.^7,8