(1) Background: Fish is a good source of protein, iron, and zinc, which are key nutrients for infant growth and development, as well as a source of energy for adults and the elderly. Due to mercury contamination in both the terrestrial and aquatic environments, there is a risk that considerable levels of mercury will be ingested by the population, causing undesired illnesses and metabolic symptoms once they reach the body. The purpose of this research was to show and emphasize the hazardous effect of mercury in diverse marine products; (2) Methods: We conducted a comparative, open, randomized, non-interventional study on a study group of 119 adults from varied social and demographic backgrounds to assess the bad repercussions of mercury poisoning from fish consumption. A questionnaire with 18 questions was prepared in order to obtain information about the impact, i.e., the dangers present in fish meat. The research was carried out in Oradea and Bihor County, Romania; (3) Results: The largest age group was between the ages of 25–34, but we had respondents from almost all age groups. Most of them considered the fish healthy (30%) and that the omega-3 fatty acids have beneficial effects on the body (25.10%). More than a half of respondents (55%) were unaware of the hidden danger in fish meat in the form of mercury derivatives. Most respondents (65%) considered that they did not consume enough amounts of fish to suffer the consequences of this phenomenon. More than a half of respondents (59%) agreed that they should have been made aware beforehand by displaying the hazards of excessive intake of some high mercury concentration fish species; (4) Conclusions: It is imperative that the population be informed about dangers of mercury toxicity when consuming fish. Mercury must be gradually eliminated worldwide by replacing it with safer alternatives.