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.

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.

There are a number of things that could cause the ship to turn around, like lack of food and water or problems with the engine.