Israeli marines boarded a French yacht headed for the Gaza Strip on Tuesday and forced it to change course and go to the Israel port of Ashdod, an Israel Defense Forces spokesman said.
The crew and passengers offered no resistance, he said.
Earlier in the day the Israeli Navy ordered the crew to leave the area. The captain was told either to go to an Egyptian port or the Israeli port of Ashdod.
The yacht's crew was warned Israeli marines would take control of the boat if they did not comply.
The Dignite Al Karama, with 16 activists and humanitarian relief supplies on board, had declared an Egyptian port as its destination when it left Greek waters on Sunday, but the crew later said they were changing course towards the Gaza Strip, hoping to arrive by Tuesday afternoon.
Gaza has been under Israeli blockade since 2007 when the Palestinian radical group Hamas took control of the enclave. Israel claims the blockade is legal and is designed to prevent arms and funds reaching Hamas.
