The data consist of test diameters of sea urchins collected from quadrats from over 600 nearshore rocky bottom sites that were sampled by scuba between 1987 and 2021. The sites are from 38 locations on the north Pacific Rim ranging from Bering Island, along the Aleutian Island chain and the Alaska Peninsula to Southeast Alaska. At each site, divers counted and collected sea urchins from quadrats placed at random distances mostly along a 20-25-foot depth contour. At a subset of sites, 40-foot depths were targeted. Urchins were counted until either 20 quadrats were sampled or about 200 urchins were collected. Collected urchins were measured on the surface with plastic vernier calipers. Quadrat size is specified in the data table but was 0.25 m2 at almost all sites. At the same sites where urchins were collected, divers counted kelps and estimated percent cover of fleshy red algae, other benthic algal cover, and non-motile invertebrates in 20 quadrats along the same depth profile. Sites were plotted at random from along the coasts of islands or areas designated. Hard substrate was targeted. Sites included here are at Adak Island, Agattu Island, Akutan Island, Alaid Island, Amchitka Island, Anangula Island, Atka Island, Attu Island, Bering Island, Chiachi Island, Chuginadak Island, Hawadax (formerly Rat) Island, Kiska Island, Kodiak Island, Mitrofania Island, Nizki Island, Ogliuga Island, Sanak Island, Seguam Island, the Semidi Islands, Shemya Island, Sitkalidak Island, Skagul Island, Tanaga Island, Umnak Island, Unalaska Island, Unga Island, Yunaska Island; Amalik Bay, Kukak Bay, and Pavlov Bay on the Alaska Peninsula; Kachemak Bay on the Kenai Peninsula; and Torch Bay, Surge Bay, and Sitka Sound in southeast Alaska. Sea urchin count data, kelp counts and bottom cover data, and site locations are presented in other tables.