To support a long-term program for sustainable management and conservation of coral reef ecosystems, from 2008, Autonomous Reef Monitoring Structures (ARMS) have been deployed and/or recovered across the U.S. Such cruises are conducted at two to three year intervals by the Coral Reef Ecosystem Division (CRED) at the NOAA Pacific Islands Fisheries Science Center (PIFSC). CRED partnered with other scientists from the Census of Marine Life (CoML) Census of Coral Reef Ecosystems (CReefs) to develop Autonomous Reef Monitoring Structures (ARMS). ARMS mimic the complexity of coral reefs to attract/collect colonizing invertebrates and provide a systematic, consistent, and comparable method to monitor cryptic reef diversity. The key innovation of this method is that ARMS sample biodiversity over precisely the same surface area in the exact same manner. Thus, the use of ARMS is a systematic, consistent, and comparable method for monitoring the cryptobiota community overtime. At specific reef sites, divers enter the water and deploy and/or recover the ARMS unit. Each unit consists of 23 cm x 23 cm gray, type 1 PVC plates stacked in alternating series of 4 open and 4 obstructed layers and attached to a base plate of 35 cm x 45 cm which is affixed to the reef. They are designed to mimic the structural complexity of a reef and attract colonizing invertebrates. Upon recovery, the ARMS unit is encapsulated, brought to the surface, and disassembled and processed onboard the research ship. Disassembled plates are photographed to document recruited sessile organisms and scraped clean and preserved in 95% ethanol for future DNA processing. Recruited motile organisms are sieved into 3 size fractions: 2 mm, 500 um, and 100 um. The 500 um and 100 um fraction is bulked and preserved in 95% ethanol for future DNA processing. The 2 mm fraction is sorted into morphospecies.