The families denounced Netanyahu’s plan to expand military operations. Yehuda Cohen, the father of Nimrod Cohen, an Israeli soldier held hostage in Gaza, said from the boat that Netanyahu is prolonging the war to satisfy extremists in his government and to prevent it from collapsing.

Israel is weighing an expansion of its armed presence in Gaza, even as military chiefs and a majority of the public oppose the idea out of concern for the fate of hostages still held by Hamas.