In conservation management, it is important to understand environmental tolerances at every stage of a species’ life cycle. As salinity is considered one of the most significant ecological stressors for marine bivalves, this exsitu study examined several larval stages of the fluted giant clam (Tridacna squamosa Lamark, 1819) exposed to hyposaline water. Late stage pediveligers or early stage juveniles survived in distilled fresh water for 10 min to 5 h, and showed no sign of injury during a 48 h follow-up period. Trochophores were able to survive for 10 min to 3 h in 9 ppt salinity water, and veligers were able to survive for 1 h to 42 h in 12 ppt salinity water. Results suggest that giant clam larvae in Singapore’s waters are able to survive exposure to hyposaline water such as that associated with high rainfall or river outflows.