Coal mining activity produces pollutant which is the coal dusts with heavy metals content. If the dusts mixed into the water, it will cause water pollution. Heavy metals like Pb, Zn, Cu, Cr needed by the living organisms, but if it exceeds the threshold, it will give negative impacts to the organism. Sea biota like mangrove snail (Telescopium telescopium) and mangrove crab (Scylla serrata) can be used as bio-indicators. This descriptive study aimed to determine the heavy metals content on sea bioata. Assays of Pb and Zn did on mangrove snail and assay of Cu and Cr did on mangrove crab. The heavy metals content in water performed as a comparison. There are three locations for sampling based on mangrove vegetation density which are high density, medium density, and low density. Heavy metals content test was done using Inductively Coupled Plasma (ICP) tool. Water quality standard based on South Kalimantan’s governor regulation (No. 5) 2007, and heavy metals content on sea biota based on Indonesia National Agency of Drug and Food Control (Balai POM) No 03725/B/SK/VII/1989. Specific for Cr based on Food and Drugs Administration (FDA). The results showed Cu accumulated over the threshold on mangrove crab in low density mangrove vegetation. Heavy metals content of Pb, Zn, and Cr on sea biota below the threshold. Heavy metals content on water also below the threshold. The study was conducted in physical environments that can be tolerated by sea biota.