The Moskalyev SAM-2, alternatively known as the MU-3, was a Soviet two seat introductory training flying boat tested in 1931. It was not chosen for production.
The SAM-2 was an extensive modification of the Grigorovich MU-2, MU standing for morskoi uchyebnyi or marine trainer. It retained the pusher configuration biplane layout, its open, side-by-side cockpit and many components. New features were an improved hull underside, or planing bottom, smaller wings and a much lighter structure.
It was completed in February 1931 and was officially tested in the spring. These led to its abandonment in favour of the parasol wing Shavrov Sh-2 amphibian which was built in large numbers, some active as late as 1964.