The U.S.-Iran deal due to be signed Friday may offer some hope for tens of thousands of commercial sailors trapped in the Strait of Hormuz, but it's unlikely to quickly end what for many has been a brutal ordeal.

"It is, at best, the beginning," the International Transport Workers' Federation, a global association of transport workers' unions, said in a statement Monday.

Both Iran and the U.S. have detained and attacked commercial vessels accused of transgressing regulations imposed on the Strait of Hormuz and surrounding waters during the 109-day war. 

At least 14 commercial mariners have died during the war, including three Indian nationals killed in a U.S. strike on an Iranian tanker last week. Others have been wounded, detained by military forces or stuck at sea in hellish conditions.

About 600 vessels remain trapped in the Persian Gulf, according to business intelligence firm Kpler, and shipping companies expect it to take weeks — if not months — for normal traffic through the Strait of Hormuz to resume. The narrow strait is the only way in or out of the Gulf.

While there is cautious optimism, evacuation and repatriation of the workers on the stranded ships does not appear imminent.

"Words on paper must now translate into action for the transport workers who have paid the price of this conflict," said the International Transport Workers' Federation, adding it was already working on evacuation plans with the U.N.'s International Maritime Organization.

"Our hearts are shattered"

Many of the mariners stuck at sea are Indian nationals.

Conditions on ships around the Gulf were "unbearable" last week, as U.S. strikes on three commercial vessels left the three Indian nationals dead, according to Manoj Yadav, general secretary of the Forward Seamen's Union of India.

"They were absolutely not feeling well. Many called us and said they are not able to sail further," Yadav told CBS News in a Monday phone interview.

India's commercial shipping ministry said this week that nearly 18,000 Indian mariners remain in the region, and Yadav said many had "expressed they are feeling like [they are] in jail."

A fourth Indian mariner, Second Officer Nishanth Uirthanathan, died on board the MT Celestial Sea tanker last week, about a month after the U.S. Navy diverted the vessel, according to the Indian seafarers union. The Iranian-flagged ship had been bound for India, but was rerouted by some 400 miles to Oman's Duqm Port, the union said, where Uirthanathan died on June 11 while awaiting medical evacuation. 

His body remained on board the ship for three days without refrigeration, Yadav said Monday.

The U.S. military's Central Command said on May 20 that forces had boarded the Celestial as it was "suspected of attempting to violate the U.S. blockade by transiting toward an Iranian port." 

The U.S. forces "released the vessel after searching and directing the ship's crew to alter course," CENTCOM said at the time. 

Seafarers left trapped by the conflict have faced shortages of food, water and medical care on their vessels, as well as the threat of attacks. 

"The seafarers were the sufferers," Yadav said.

Some Indian nationals have managed to abandon their ships near enough to Iranian ports to make their way back to India by land, albeit without their wages, he added.

Mariners on U.S.-sanctioned vessels such as the MT Marivex, which was struck by the U.S. on June 9, may not even be aware the ships they're on are subject to sanctions.

"They are just looking, what are the size of the vessel, where are the trading areas, and how much salary they will get," Yadav said. "That is their primary need, rather than finding out whether it is [sanctioned] or not."

CENTCOM has "disabled" nine ships for failing to comply with its blockade and turned back 135 others, it said.

Yadav said the U.S. could have struck the ships in a way that avoided casualties, and the union has demanded that the United Nations investigate the strike on the Marivex — and that the U.S. government pay at least $5 million in compensation to the families of the three mariners killed in the strike on the Palau-flagged M/T Settebello and the fourth who died on the Celestial Sea.

"We want to know the full truth of what happened," the grandfather of one of the men who died on the Settebello, Aditya Sharma, told the Press Trust of India. "Our hearts are shattered."