No, it is toxic, causing convulsions, dehydration and death in mammals.
The toxicities of Na+, Cl- and Mg++ ions in sea water and in artificial solutions were investigated. Convulsions commonly followed intraperitoneal injection of hypertonic salt or sucrose solutions in rats, but the convulsions due to sea water and NaCl solutions differed from sucrose or urea convulsions. Respiratory distress preceded death. Even in thirst, little sea water was taken voluntarily. Salt solutions or sea water given by stomach tube caused dehydration. Plasma Cl- concentrations reached the same low level after lethal doses by either route. Dogs and seals vomited sea water from the stomach. Seals were not more resistant than the other mammals. The lethal dose of sea water for rats was decreased by previous dehydration. Some adaptation appeared after repeated sublethal doses.
—Toxicity of sea water in mammals by ALBRECHT, C. B., Journal
American Journal of Physiology 1950 Vol. 163 pp. 370-385
It's a well cited 1950's article so I assume it's fairly authoritative.