Abstract: A stair portion for a stair assembly for a swimming pool, comprising a bottomless hollow body having lateral surfaces and a top surface defining steps. The bottomless hollow body is adapted to be received in a pool with bottom edges of the lateral surface lying against a bottom of the pool such that a user person can move in or out of the pool using the steps. The bottomless hollow body is adapted to be connected to a pool connector portion for being secured adjacent to a sidewall of the pool. The bottomless hollow body is adapted to be nested with another bottomless hollow body, so as to facilitate transportation, warehouse storage or maneuverability in a body of water.