The hatchability, mortality rate, lipid peroxide levels, and swimming speed of Artemia salina have been compared based on short exposures of ZnCl2, CdCl2, and HgCl2 in artificial seawater. The hatching tests were carried out for 12, 24, 36, and 48 h at 28 °C. Mortality rate and lipid peroxide (LPO) levels were determined after 24 h of exposure at 28 °C, in the dark, and on living larvae using the FOX method. The swimming speed was determined after 24 h using a microcomputer coupled to a digital camera, with simultaneous treatment of the recorded images every 25 s, at 25 °C, under red-light irradiation. Results showed that Zn caused a gradual inhibition of the hatching for concentrations <900 µmol L−1; however, Cd and Hg displayed almost complete inhibition for concentrations ≤100 µmol L−1. Also, the heavy metals caused a dose-dependent increase of mortality (LD50) in the following order: Zn = 3290 µmol L−1 < Cd = 2206 µmol L−1 < Hg = 15.6 µmol L−1. Furthermore, significant LPO levels were found for Cd (1500–2000 µmol L−1, p < 0.001) and Hg (5–20 µmol L−1, p < 0.001). Finally, the swimming speed values increased significantly, for Zn ≈ 2.5 mm s−1 (1500 µmol L−1, p < 0.001), Cd ≈ 3.5 mm s−1 (2000 µmol L−1, p < 0.05), and Hg ≈ 4.0 mm s−1 (15 µmol L−1, p < 0.05), after 24 h exposure. There is a clear dose-dependent toxicity, indicating that Zn, Cd and Hg can induce significant changes in hatchability, mortality, and ethological and biochemical parameters.