The concept, introduced in Shanghai on March 26, is aimed at ensuring less space is used in city graveyards, China Daily reported.
The first three families to choose a partial sea burial scattered about 99.5 percent of their loved ones' ashes in the ocean during the annual public memorial for sea burials, which took place at Binhaiguyuan Cemetery in Fengxian district, Shanghai.
The memorial garden contains a monument carrying the names of almost 2,000 people whose entire ashes have been scattered at sea.
"We introduced the partial sea burial as a new concept, also a mid-point between traditional burials and sea burials," Zhao Xiaohu, the manager of Binhaiguyuan Cemetery, said.
"We keep a small amount of ash in a container as large as a matchbox that will decompose in the ground along with the ash after being buried," Xiaohu revealed.
Xiaohu added that he and his team at the memorial garden, which was established in 2004 for families choosing burials at sea, will recommend partial sea burials to families because of the environmental benefits.
The practice started to take off in the metropolis in 1991, when the ashes of 287 people were scattered at sea. The number had risen to 2,100 by 2010.
"Despite the rise in the number of people accepting sea burials, we would still like to see more people choose this environmentally friendly method," Zheng Jixiong from the Shanghai Feisi Sea Burial Company said.
"Residents' awareness and acceptance of sea burials have increased significantly during the past two decades," Jixiong stated.
During the past 20 years, the city has organized 162 collective sea burial ceremonies, scattering more than 21,100 caskets of ashes.
But, while about 80 percent of Shanghai residents are cremated, only a very small number of them choose to have their ashes scattered at sea, despite it being the cheapest option.
"The city has simply run out of large, open spaces for cemeteries. If we keep allowing individual plots to take up 1.5 square meters there will be no land left in less than 10 years," Xiaohu said.
The country's growing population has made its land increasingly precious, especially in large and medium-sized cities. At least 20 million graves are dug nationwide each year, occupying about 67 square kilometres.
"Land is becoming so scarce that if we don't make the cemeteries more efficient soon, there will be no space left and everyone will have to scatter their ashes into the ocean," Xiaohu added.