The Cayman Islands are served by Flow (Liberty Latin America) and Digicel. Both operators provide 4G LTE on Grand Cayman with strong coverage across George Town, Seven Mile Beach, and the main island roads. Flow also operates in Cayman Brac.
Grand Cayman has reliable 4G across the entire main corridor from the airport to George Town and along Seven Mile Beach. The eastern end of the island and Bodden Town are also covered. Stingray City sandbar in the North Sound area has signal from shore, though the sandbar itself is in open water where signal may vary.
Cayman Brac has some 4G coverage in main areas. Little Cayman is very small (about 60 residents) and has limited coverage. The dive sites around all three islands are accessed by boat, and open water loses signal quickly. Download offline maps and dive site information before any boat trip. Grand Cayman's interior (if exploring mangroves or the Mastic Trail) has coverage since the island is small enough for tower reach across most terrain.