New York's Times Square may be getting a new tenant: a seven-story aquarium.

Jerry Shefsky, a Toronto-based developer, said on Wednesday that he has signed a preliminary agreement with the landlord of an office tower on the western edge of Times Square to go forward with the $100 million project. He would install tanks featuring sharks, rays, penguins, otters, and other animals in the bottom floors of the 40-story building, known as 11 Times Square, hoping to attract some of the 35 million people who pass through Manhattan's major crossroads every year.

Mr. Shefsky, 76 years old, has built aquariums and shopping centers around the world. He cautioned in an interview that the lease agreement for 11 Times Square isn't yet final. But he said he may start building out the space as early as this April with the hope of opening the aquarium in September 2011.

A deal with Mr. Shefsky would be a long-awaited bit of good news for the developer of 11 Times Square, SJP Properties Inc., and its major financial backer, a real-estate fund managed by Prudential Financial Inc. SJP, led by New Jersey developer Steven Pozycki, broke ground on the tower in 2007 without having first secured a tenant, hoping that the hot Manhattan office market would bring sky-high rents as the building neared completion. But the market turned—New York City office rents plummeted 20% in 2009, according to Reis Inc.—and SJP's empty tower on the corner of 42nd Street and 8th Avenue has become a symbol of commercial-property woes.

SJP is also negotiating to lease 400,000 square feet in the building to law firm Proskauer Rose LLP, said a person familiar with the matter. The building is slated to be completed in the next few months.