Sinkhole divers. Some of the most spectacular are the Zacatón cenote in Mexico (the world's deepest water-filled sinkhole), the Boesmansgat sinkhole in South Africa, Sarisariñama tepuy in Venezuela, the Sótano del Barro in Mexico, and in the town of Mount Gambier, South Australia. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as blue holes and often become popular diving spots. Large and visually unusual sinkholes have been well-known to local people since ancient times. Nowadays sinkholes are grouped and named in site-specific or generic names. Some examples of such names are listed below. The
DNS sinkhole DNS sinkhole A DNS sinkhole, also known as a sinkhole server, Internet sinkhole, or Blackhole DNS is a DNS server that gives out false information, to prevent the use of a domain name. A sinkhole is a DNS provider that supplies systems looking for DNS information with false results, allowing an attacker to redirect a system to a potentially malicious destination. DNS sinkholes have also historically been used for non-malicious purposes. When a computer visits a DNS source to resolve a domain name, the provider will give a result if possible, and if not, it will send the resolution system