While social and cultural core values have been increasingly recognised in marine biosecurity risk assessment, biosecurity decision-making generally rely upon data derived from institutional led (top-down) practices, with societal perception and values that are hazard- or threat-focused rarely addressed in the same context. Working on a collectively rich dataset with 2469 value statements from 1001 survey respondents (the general citizens, or the ‘novices’), and 72 values statements from 14 scientists and managers (the ‘experts’), we aim to identify and compare aspects of marine, beach, and coastal areas that were personally important to general citizens, who are unfamiliar with the marine biosecurity and value concepts, and those perceived by experts, who have a strong scientific background and are involved actively in marine biosecurity activities, either in research or policymaking. Our findings reflect a considerable schism in value perceptions between experts and general citizens in terms of communication linguistics, and value conceptualisation and scales. Our comparative study highlights the risks of subjective biases in policy-relevant expert judgement elicitations regarding social and cultural values, and the potential of unawareness (or ignorance) of citizens’ values, which may lead to overlooking hidden but real concerns of citizens in biosecurity policymaking in a dynamic context like marine and coastal areas. To this end, we suggest a collective approach where a general public’s value system is incorporated with experts’ knowledge and judgements for (marine) biosecurity risk assessment and management.