Many more than I thought - 1 in 5

Ten days ago, I saw that there were a lot of ships holding off the port of Shanghai, China.
Here is the image from shiptracker live which tracks each vessel's AIS data:

The numbers are a lot bigger than I thought. From Fortune:

China’s COVID-19 lockdown is inflaming the world’s supply chain backlog, with 1 in 5 container ships stuck outside congested ports
After the pandemic, and the chip crisis, and the war in Ukraine, “disrupted” seems to be the default state of global supply chains. But the pandemic isn’t over yet, and a COVID outbreak in China is only making supply constraints worse.

According to shipping analytics firm Windward, 20% of the world’s roughly 9,000 active container ships are currently sitting in traffic jams outside congested ports. Close to 30% of that backlog alone is in China—double the domestic congestion rate in February—where a virulent Omicron wave is snarling supply lines.

Ships have been piling up outside Shanghai, the world’s largest port, and other container docks across China as authorities have forced multiple cities into lockdown to counter the country’s worst COVID outbreak since the pandemic began.

Shanghai has been under lockdown for close to four weeks, having recorded over 35,000 COVID cases since March. Residents in the city of 25 million have struggled to secure food and access to health care as authorities prohibit them from leaving their homes.

I doubt it's covid.  China is up to something nefarious and this is just the tip of the iceberg.