MILAN — A life on the seas, including two circumnavigations of the globe, has given U.S. yachtsman Paul Cayard a first-hand view of the increase of plastic waste in the world’s oceans.

Cayard said Tuesday at a forum on preserving oceans that over his 50-year sailing life, including seven Americas Cups and seven world championship titles, he has witnessed everything from plastic bags caught on racing boats in the high seas to refrigerators and sofas floating in the bay off Rio de Janeiro.

On a recent race from Los Angeles to Hawaii “half the boats had problems with plastic getting stuck on the keel, and they either have to stop and go backward to get it off, or send someone overboard,” said Cayard, 58.

While it is frustrating from a racing perspective, he said the bigger issue “is just how bad this is for the planet.”

The One Ocean forum aims to bring together interested parties to tackle how to preserve the marine environment. Promoted by the Yacht Club Costa Smeralda on the Italian island of Sardinia, partners include UNESCO and Milan’s Bocconi University.

Francesca Santoro, an oceanographer in UNESCO’s oceanography commission, said the forum hopes to promote solutions that can be measured over time. One proposal during this, the inaugural forum, is aimed at mobilizing scientists, artists and the media to raise awareness about threats to the ocean environment.

She said the ocean has not been high on the agenda of international policy, and few are aware that it generates half of the oxygen we breathe through the same process of photosynthesis on phytoplankton that occurs with plants in forests.

“The ocean is something that is not visible. We only see the surface. We don’t think about the deep ocean,” she said.

The amount of plastic in the oceans remains a huge issue, with over 8 million tons of plastic entering the seas each year, 80 percent from land, she said.

Tackling that means sensitizing people to avoid one-use plastic, including bottles and straws, and lobbying companies to stop using plastic where other materials can be substituted, such as on cotton swabs.

Cayard said on the last Americas Cup race, plastic bottles were banned, so the teams had to fill reusable water bottles from a big container on board.

“We were trying to do our part to cut down on the consumption of plastic,” he said.