Marevivo is a significant Italian environmental association that protects the sea and its resources, focusing in particular on biodiversity conservation, sustainable development, enhancement and promotion of marine protected areas, combatting pollution and illegal fishing. They promote education in schools and universities, and act as an advocate influencing law and policy with many successful campaigns in Italy, such as recently the ban of microplastics in rinse-off cosmetics and the ban on sea cucumber fishing. Marevivo relies on the work of hundreds of volunteers and thousands of members scattered all over Italy, with representation throughout the country in the form of delegations in more than 25 centres. They are organised into diving, sailing, canoe & kayak, beaches and shore divisions.

Marilles Foundation is dedicated to the conservation of the Balearic Sea and its coasts, and reconciling the conservation of marine ecosystems and economic prosperity. Working other foundations and private donors, their main source of funding comes from the Adessium Foundation. They coordinate local efforts and finance the most effective measures to conserve the Balearic Sea, including connecting those most prepared to carry out marine conservation projects with those who can finance them. Currently, their priorities are to: improve marine protected areas; secure sustainable fisheries; and promote marine education. They also support projects that reduce the impact of the boating and tourism industries, and of plastics and pollution.

The Marine Biological Association of the United Kingdom is a learned society with a scientific laboratory that undertakes research in marine biology. The organisation was founded in 1884 and has been based in Plymouth since the Citadel Hill Laboratory was opened on 30 June 1888. Amongst its projects is the MarLIN project

The Marine Cleanup Initiative was founded by volunteer scuba divers who collect waste from the ocean. They are active in Florida.

Marine Connection was founded in 1997 after being directly involved in campaigning against, and successfully closing down, the last dolphinariums in the UK. The charity is dedicated to the protection, conservation and welfare of dolphins, whales and porpoises – securing a safer future for cetaceans across the globe. It addresses many of the threats these marine mammals face, lobbying governments and liaising with decision-makers to create or change legislation laws to ensure better protection for cetaceans – both in the wild and in captivity.

The Marine Conservation Action Fund (MCAF), part of the New England Aquarium, is a microgranting program that addresses critical needs in the marine conservation field, by funding small-scale, high-impact projects around the globe. With each funded project, MCAF is helping to protect the health of marine species and habitats, and the communities that depend on them in low and middle-income countries. Since 1999, MCAF has supported many various projects, including researchers gathering key data on threatened and endangered animals, grassroots leaders engaging and educating communities through local conservation projects; and efforts to offer long-term protection for marine species and habitats.

Marine Conservation Alliance promotes healthy oceans and sustainable fisheries to feed the world. It is a community of concerned individuals that believe in science-based management and progressive projects that promote stewardship, healthy oceans and sustainable fisheries.

Marine Conservation Cambodia is a fully licensed research facility specializing in seahorse research in Cambodia, as well as research into the surrounding reefs and benthic areas. Based on Koh Ach Seh in Kep Province.

Marine Conservation Costa Rica is dedicated to ocean conservation through action and education. Their projects include Coral Restoration, Reef Health Surveying and Marine Education. They offer two day marine conservation courses through to month long internships where the participants learn and have hands on experience in all aspects of running a coral restoration project.

Marine Conservation Institute is a non-profit scientific and conservation advocacy organization that has been working since 1996 to promote cooperation essential to protecting and restoring the Earth's biological diversity. From the headquarters in Seattle WA and the Washington DC and California offices, they work to protect marine life around the United States and beyond by encouraging research and training in marine conservation biology, bringing scientists together to examine crucial marine conservation issues, conducting policy research to frame the marine conservation agenda, leading outreach efforts to educate scientists, the public and decision makers on key issues, and building partnerships to solve problems affecting marine life and people.

The mission of the Marine Conservation Network is ‘to build a global size ocean community by closing the communication gap between scientists, conservationists, and the general public.’ This includes better communication and understanding among scientists, conservationists, and the public by establishing a shared platform for collaboration in pursuit of conservation and scientific advancement. This is aimed at addressing, together, the challenges facing the oceans today, including climate change, overfishing, plastic pollution, and habitat destruction. Their goal is to raise awareness, promote sustainable fishing practices, protect critical habitats, and ensure the health and resiliency of marine ecosystems. This includes sharing information and resources, including video resources, as well as advocating for policies and actions.

Marine Conservation Northern Ireland are lobbying our Government to present the argument for the protection and promotion of fish stocks for the purpose of recreational Sea Angling (RSA), initially through the implementation of marine protect areas(MPA’s).