According to the Marine Executive, the boat “corresponds to a UK-registered 18-meter sailing vessel named Barcarole.”The vessel left port on Sunday on what is thought to be an estimated 2,000-kilometer trip.

Thunberg and 11 other activists are on board a ship headed to Gaza with aid supplies, but the IDF has said it does not intend to allow the ship to dock.

The almost 20 months of war has torn Gaza apart, often displacing residents multiple times and killing more than 54,000 people, according to the Hamas-run Health Ministry. A U.S.-brokered ceasefire agreed in January collapsed in March as Israel enforced a blockade on all humanitarian aid into the strip.