CULLY, Switzerland (AP) _ Three decades after he and a U.S. Navy officer set a world record by diving as deep in the sea as jetliners fly high in the sky, the Swiss deep-sea researcher Jacques Piccard has designed a submarine for tourists.

It will be launched in the spring by a private company and will offer passengers ''an uncommon way to share the riches of the sea.''

The $4-million craft, which will seat 16 people and a crew of two, is nearing completion at a Swiss plant in Winterthur.

It will be somewhat roomier than the bathyscaph ''Trieste'' that went down 32,748 feet to Challenger Deep at the bottom of the Marianas Trench in the Pacific on Jan. 23, 1960, with Piccard and Lt. Don Walsh on board.

Exploring life underwater has since filled most of the 67-year-old Piccard's life. He has done research for universities, governments, and the police, collecting marine samples, and checking up on underwater pipelines.

''We have found everything from automobile tires to aircraft down there,'' he said.

He still boards his small ''working sub'' about twice a week, diving in Lake Geneva, Western Europe's largest freshwater body.

Launched in 1979, the sub named after the Swiss scientist F.A. Forel has been used on scientific, industrial, and recovery missions in many European lakes as well as in the Mediterranean.

In 1969, Piccard and five other scientists spent a month exploring the Gulf Stream in the mesoscaphe Ben Franklin, also designed by him. But he says none matched the experience he had on his world record dive.

''By far the most interesting find was the fish that came floating by our porthole at the bottom of the Challenger Deep,'' he said in an interview. ''We were astounded to find higher marine life forms down there at all.''

Having more people share the riches of the sea is an idea initiated by his father, Auguste Piccard, who also made scientific history in the stratosphere in the early 1930s, ascending 50,400 feet in a balloon of his own design.

''I came up with the idea of sending tourists underwater and it was my father who designed the world's first tourist submarine,'' Piccard said.

During the Swiss National Exhibition in 1964, the father's submarine carried more than 30,000 people to the depths of Lake Geneva.

Jacques Piccard's new 33-ton, 40-foot PX44 has several more sophisticated features and more advanced electronic equipment than his father's.

It will cruise at three miles an hour and be capable of diving to 300 feet on tours of up to 40 minutes, Piccard said.

Powerful searchlights and large portholes will bring the depths of the sea to brilliant life for the passengers entering the world of scuba divers in relaxed, first-class comfort.

But for Piccard, the PX44 will also help bring greater awareness of the environmental threats to the world's seas.

''For me, the more people discover the sea, the greater the chance of bringing marine issues into public view and the better off we will all be,'' he said.