Fraser's dolphins swim in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

An aerial drone photo shows short-finned pilot whales swimming in the waters east of Hainan Island, south China, July 5, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Fraser's dolphins swim in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

An aerial drone photo shows short-finned pilot whales swimming in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

A short-finned pilot whale swims in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Short-finned pilot whales swim in the waters east of Hainan Island, south China, July 5, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

An aerial drone photo shows short-finned pilot whales swimming in the waters east of Hainan Island, south China, July 5, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

An aerial drone photo shows short-finned pilot whales swimming in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Members of a marine biodiversity expedition team take photos on deck in the waters east of Hainan Island, south China, July 5, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Members of a marine biodiversity expedition team observe on the prow in the waters east of Hainan Island, south China, July 5, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Members of a marine biodiversity expedition team observe on deck in the waters east of Hainan Island, south China, July 5, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

An aerial drone photo shows Fraser's dolphins swimming in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Fraser's dolphins swim in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)

Short-finned pilot whales swim in the waters east of Hainan Island, south China, July 6, 2024.

A marine biodiversity expedition team has recently witnessed a large number of cetaceans in the waters east of Hainan Island, including short-finned pilot whales, Fraser's dolphins and rough-toothed dolphins. Among the cetacean species, many mother-child pairs have been spotted. (Xinhua/Zhang Liyun)