Volunteer divers participating in the Reef Life Survey (RLS) program actively assist species conservation efforts by generating data for threat assessments and population trend monitoring, through in-water restoration efforts, and through outreach of marine conservation messages. Up to 2014, standardised underwater visual survey data provided by RLS divers described densities of 495 cryptic fish species at over 1200 sites distributed around Australia. Each species was recorded on 34 separate transect blocks on average, allowing the first assessments of population trends for many species. These data highlight the threatened and data deficient status of endemic Australian handfish species. At least five shallow-water handfish species are potentially threatened, including the smooth handfish Sympterichthys unipennis, which has not been sighted for over 200 years, but is yet to be included on any threatened species list. RLS divers undertook directed searches at key historical locations for two handfish species, the red handfish Thymichthys politus, now only known from a single reef, and Ziebell's handfish Brachiopsilus ziebelli, with no confirmed sighting for over a decade. From a total of 100 h of underwater search effort, only four red handfish were recorded, all at a site threatened by adjacent human activity. These and other handfish species should be considered for inclusion on the IUCN Red List given that populations are either very small or have vanished, spawning substrates have probably declined, and the species lack a larval dispersal stage. More importantly, the absence of information on the conservation status of the majority of marine species needs urgent attention, including through expanded citizen science efforts, if management intervention is to occur and extinctions minimised.