Alexeyev was an accomplished designer of hydrofoil ships, such as the Raketa, and became a prominent developer of ground-effect vehicles, particularly the Caspian Sea Monster and the A-90 Orlyonok.

Rostislav Evgenievich Alexeyev was born on December 18, 1916, in Novozybkov, Chernigov Governorate, Russian Empire (now in Bryansk Oblast, Russia) to an agronomist father and a teacher mother.

In 1962, Alexeyev began working at the Central Hydrofoil Design Bureau which specialized in the secret development of ground-effect vehicles, named ekranoplans.

Ground-effect vehicles were technically aircraft, but operated using ground effect to travel only several meters above flatter surfaces, particularly bodies of water, leading them to be classified as ships by the Soviet government.

Only two years after development began the project resulted in the Korabl Maket (KM), better known in English as the Caspian Sea Monster, with Alexeyev as the chief designer and V. Efimov as the lead engineer.

The KM was at first seen as a promising vehicle specialized for use by military and rescue workers but its design caused many difficulties, progress slowed and Alexeyev quickly moved on to other ekranoplan projects.