Turkey has backed Qatar after Saudi Arabia, Egypt and other Arab states cut all economic and diplomatic ties this month, accusing Doha of supporting terrorism, a charge it denies.
A ship carrying 4,000 tons of food for beleaguered Qatar left Turkey early on Thursday.
The vessel marked a change in how essential supplies are being sent to Qatar after it departed the western city of Izmir which housed aid planes to deliver essential supplies, such as dry food, fruits and vegetables.
Qatar, a small peninsular Gulf state, is struggling to maintain food supplies because of the "embargo crisis", as its land border with Saudi Arabia is now closes, said the chief executive of the logistics company behind the shipment.
Ipek Demirci said a sea route had been opened because air transport was insufficient to meet the needs of the Qatari population.
She also said her firm was preparing to send a second ship in the coming days.
TRT World's Abubakr Al Shamahi has more.
105 cargo planes
So far, 105 cargo planes from Turkey have carried aid to Qatar, Ankara's economy minister, Nihat Zeybekci, said on Wednesday.
On June 5, Saudi Arabia, Egypt, the United Arab Emirates (UAE), Bahrain and Yemen abruptly cut diplomatic relations with Qatar, accusing Doha of supporting terrorism.
Mauritania followed suit shortly afterward, and Jordan closed the local office of Qatar's Al Jazeera satellite news channel.
Saudi Arabia, the UAE and Bahrain also closed their airspace to Qatari aircraft, and gave Qatari diplomats 48 hours to leave their respective countries.
Riyadh sealed its land border with Qatar, geographically isolating the small country.
Other countries to have recently cut diplomatic ties with Qatar include the Maldives and the Comoros Islands, along with Libya's Tobruk-based government, which supports General Khalifa Haftar and lacks international recognition.
Qatar denies all accusations that it is a supporter of terrorism, describing moves to isolate it by its fellow Arab countries as "unjustified".
List of demands
United States says Saudi Arabia and its allies will soon present Qatar with a list of demands meant to resolve the dispute.
The list has been coordinated by Saudi Arabia, the UAE, Egypt and Bahrain.
In a statement, US Secretary of State Rex Tillerson said he hopes those demands will be 'reasonable and actionable.'
Turkey and Kuwait have been leading mediation efforts.
On Wednesday, Turkish President Recep Tayyip Erdogan spoke with Saudi Arabia's King Salman and the new crown prince Mohamed bin Salman. They have agreed to step up efforts to diffuse the crisis.
TRT World's Soraya Lennie explains from Doha how the blockade of Qatar by the neighboring Arab countries has affected the country's construction industry.