Ocean Exploration Trust and the Nautilus Exploration Program, under the direction of Dr Robert Ballard, seek out new discoveries in geology, biology, and archaeology while conducting scientific exploration of the seafloor. Their expeditions launch aboard Exploration Vessel Nautilus, a 68-meter research ship equipped with live-streaming underwater vehicles for scientists, students, and the public to explore the deep sea from anywhere in the world. Via their communications and education capabilities, they communicate their experiences live as they explore seascapes never seen before, aiming thus to inspire people to care about the oceans and to aspire to ocean exploration. The vessel E/V Nautilus's home port is at the AltaSea facility in San Pedro in the Port of Los Angeles, California.

The Ocean Health Index is a valuable tool for the ongoing assessment of ocean health. Using a quantitative, comprehensive method, the index evaluates the ecological, social, economic, and political conditions for the coastal waters of the world’s 221 countries and territories with ocean shorelines. This provides a means to analyse the state of the oceans, and thus it enables comprehensive ocean policy, at the same time providing a comparative measure, thus informing decisions about how to use or protect marine ecosystems. The Index is a collaborative effort, made possible through contributions from more than 65 scientists/ocean experts and partnerships between organizations including the National Center for Ecological Analysis and Synthesis, Sea Around Us, Conservation International, National Geographic, and the New England Aquarium.

OMI's objectives are to change people's awareness to better understand the natural world, and to protect ocean mammals. OMI's programs have three goals: To study the impact of human marine activities including noise pollution on whales and dolphins; to apply the results of research to protecting marine mammals and their environment; to allow people to participate fully in their research in order to educate them about important conservation issues and empower them to act responsibly. By doing research to protect the whales and dolphins, people learn they can help preserve biodiversity, including by addressing the problem of pollution. Operates in the US, Alaska and Hawaii

Ocean Missions 'inspires people to take direct action towards ocean conservation by an excellent combination of science, education and adventures program during seasonal expeditions in Arctic regions onboard Schooner Opal in collaboration with NorthSailing'.

ORCA describes itself as a technology-based marine conservation association. Their strategy is to collect accurate and scientifically defensible data on water quality and its impact on marine ecosystems, to provide the data to the public and decision makers in an easily accessible and understandable format, and to engage communities in marine conservation action, with positive reinforcement for their efforts through feedback involving easily understandable scientific data. Focus of research is on the Indian River Lagoon.

ORE focuses on two program areas with a strong focus on coral reefs, amongst others: 1. Ocean Research and Exploration Program: promotes the scientific inquiry by supporting field-based research and investigations that span broad geologic time-spans and across multidisciplinary fields. One of the cornerstones of ORE’s research programs has been Dr. Ginsburg’s establishment and operation of the Atlantic and Gulf Rapid Reef Assessment Program (AGRRA) which focuses on the understanding and protection of coral reefs. Additional projects have included the use of submersibles to explore deep sea corals and the investigation into shallow water stromatolites – Earth’s oldest fossils. 2. Ocean Education and Inspiration Program.

Ocean Spirits is a registered, non-profit marine conservation organisation based in Grenada, focused primarily on the conservation of marine turtles. Their projects involve research on the local turtle populations with the aim to protect them, education and engagement with the local community in order to sustain the turtle populations and to combat turtle egg harvesting. Ecotourism forms part in their conservation initiatives.

A global conservation organization, Ocean Wise operates an number of programmes involving research and education regarding the threats facing the oceans, such as Ocean Wise Seafood which is a sustainable seafood program, Sea forestation which involves restoring, planting, managing and caring for underwater seaweed forests, their Cleanup programme and plastic pollution initiative, marine research and education

Oceanites provides scientific data and recommendations for the conservation of Antarctica, utilizing penguins to help understand the impact of climate change. Since 1994, Oceanites has been analysing penguin and seabird population changes across the vast Antarctic Peninsula, where it’s warming faster than anywhere else on Earth except the Arctic. The organisation represents the world’s only non-profit, publicly supported Antarctic research programme.

Oceanologico conducts interdisciplinary research in the fields of marine biodiversity, environmental pollution (microplastics) and the relationship between humans and the ocean on the island of La Palma in the Canarian Archipelago. They also conduct snorkelling and diving tours and have an overall aim of improving ocean literacy generally.

Oceanomare-Delphis research and monitor cetaceans in the Mediterranean, with aim of conserving cetaceans and marine biodiversity. The focus is on non-invasive studies, promoting education and conservation programmes and enhancing public awareness of, and concern for, cetaceans and the marine environment. ODO advocates for financial support of scientific and conservation programmes and facilitates dissemination of results through professional networking, capacity building, public outreach and scientific publications. The organisation believes the application of scientific knowledge to management and policy is essential for effective cetacean conservation. The Ischia Dolphin Project is one of their many initiatives.

With offices in Ottawa, Winnipeg and Halifax, Oceans North supports marine conservation in partnership with Indigenous and coastal communities. Their science- and community-based conservation in the Arctic regions of Canada and Greenland has the goal to promote policies and programs that address the unprecedented environmental changes taking place in the North and ensure that its waters are protected within the framework of Inuit knowledge, rights and consultation.