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 to a higher-level provider to try again. The higher a DNS Sinkhole is in this chain, the more requests it will receive, and the more impactful it will be. A sinkhole is a standard DNS server that has been configured to hand out non-routable addresses for all domains in the sinkhole, so that every computer that uses it will fail to get access to the real website. The higher up the DNS resolution chain the sinkhole is, the more requests it will block as it will supply answers to a greater number of lower NS servers that in turn will