The Israeli navy intercepted a ship off the Lebanese coast, confiscated a cargo of weapons destined for Palestine Liberation Organization guerrillas in Lebanon and arrested one person, an Israeli military spokeswoman said in Tel Aviv. She said the ship aroused Israeli suspicions because it had a speedboat on deck when it was spotted by Israeli patrol boats Aug. 30. Similar craft have been used to land guerrillas in Israel. The weapons included machine guns, shells and rocket-propelled grenades and launchers. The person responsible was placed in custody and taken to Israel, she said, while the ship and its crew were allowed to continue.