The Sea of Change Foundation funds conservation and research initiatives that directly impact the marine world, including coral reefs restoration, ocean pollution, and protection of threatened species and habitats internationally.

Sea-Changers is a UK marine conservation charity, managed by a small team of volunteers who aim to protect the UK's seas, shores and wildlife. They give grants to UK marine charities and non-profits for conservation and research projects, by working with businesses and individuals to raise funds via bespoke corporate partnerships, online giving, eBay auctions, sponsored events and individual donations.

Sealegacy involves a group of experienced and renowned photographers, filmmakers, and storytellers who work towards making the oceans healthy and abundant. There has been some controversy about this group, with the scientific community questioning the veracity of their work.

A programme of Sustainable Surf, a California-based non-profit organization, SeaTrees is working to plant one million “sea trees”—mangroves and kelp—to fight climate change. Their stated mission is to 'protect and restore coastal ecosystems globally, to protect ocean health and fight climate change. Their projects include mangrove planting in Asia, Africa, and the US, and coral restoration initiatives in Asia.

Seacology’s mission is 'to protect threatened island ecosystems all over the world'. This they do by working directly with communities, helping them to preserve their cultures and improve their lives while saving precious island habitats. Many of their new projects involve protecting key marine ecosystems—coral reefs, mangroves, and seagrass—all of that uphold biodiversity in our oceans.

Seas At Risk is an association of environmental organisations from across Europe, working together to ensure that life in our seas and oceans is abundant, diverse, climate resilient, and not threatened by human activities. Its mission is to promote ambitious policies for marine protection at European and international level. With over 30 members representing the majority of European countries

Seas The Day is a podcast produced at the Duke University Marine Lab, in Beaufort, North Carolina. Reflecting the diverse research and educational interests of faculty, students, and staff, Seas the Day covers a wide range of topics related to marine science and conservation.

Seasearch is a national project set up by the Marine conservation Society for recreational divers and snorkellers who have an interest in what they are seeing under water, who want to learn more and who want to help protect the marine environment. This they do by collecting information about marine habitats, plants and animals that they see under the water. All records created by volunteers are placed in the National Biodiversity Network database www.nbn.org.uk. The data is publicly available from the site and is used by conservation charities such as the Marine Conservation Society and Wildlife Trusts, government conservation agencies, academics and other organisations for many purposes. Via their one-day Observer course, Seasearch trains volunteers to map sea bed types and marine life, including identification and recording.

Seastainable Ventures is an infrastructure fund focused on maritime investments. They are a Venture Builder platform specialised in the creation, incubation and acceleration of business projects in the field of the blue economy (sustainable marine economy), particularly in relation to restoring and promoting marine natural capital. Their stated mission is to help society to evolve towards a model of sustainable development, protecting the oceans and preserving biodiversity for future generations.

SeyCCAT strategically invests in ocean stakeholders to develop actions to achieve sustainable blue prosperity in Seychelles. Their vision is for Seychelles’ ocean and islands to be stewarded by the people of Seychelles, generating sustainable benefits for future generations to share. We create the space for new ideas, help those ideas evolve, forge new creative collaborations, and boost individual and collective impact. The many projects they support include sustainable fishing and fisheries, biodiversity research, pollution prevention, coral monitoring, marine vegetation, education and awareness, amongst others.

Shark Stewards' mission is to restore ocean health by saving sharks from overfishing and the shark fin trade, and protecting critical marine habitat through the establishment of marine protected areas and shark sanctuaries. Founded in 2006, Shark Stewards is a leader in advocating and legislation to regulate overfishing sharks, the shark fin trade and creating marine protected areas. Project of the Earth Island Institute.

Sharklife addresses the alarming exploitation of both shark populations and ocean fisheries in South African waters, actively engaging in research and protection of many marine species. In their words, 'Research and education are the main tools we use to drive marine conservation objectives'