SAULT STE. MARIE, Mich. (AP) _ Mysterious ''small white objects,'' beer cans and remnants of gill-net fishing gear greeted scientists Tuesday as they embarked on an unprecedented submarine expedition to study the depths of Lake Superior.

''I think everything went as we expected,'' David Long, an associate professor of geochemistry at Michigan State University, said from aboard the research ship RV Seward Johnson. ''Things are running pretty smoothly right now. The lake looks beautiful.''

Two scientists and two crewmen descended into Whitefish Bay during the morning in the Johnson Sea-Link II, which will be ferried across the world's largest freshwater lake over the next four weeks by the Seward Johnson.

The researchers planned to test equipment, including a clawed, mechanical arm, to be used in obtaining sediment and water samples during the voyage which is to include a dive to 1,333 feet, the deepest point in the Great Lakes.

The $500,000 expedition is sponsored by the National Oceanic and Atmospheric Administration and is the agency's first venture into the Great Lakes, according to William Cooper, a Michigan State zoologist.

The four-man, battery-powered Sea-Link II made its first dive to 55 feet, then on a second dive went all the way to the bottom of the bay, 150 feet deep at that point, he said.

Michigan State zoology professor Paul Groll and Ray Argyle, a U.S. Fish and Wildlife Service researcher, were on Tuesday morning's dives.

Groll told The Associated Press in a radiotelephone interview from the Seward Johnson that he spent nearly three hours searching unsuccessfully for gill nets lost by commercial fishermen. Researchers hope to determine the derelict nets' effect on the fish population.

Long said the researchers did locate broken, 20- to 30-foot-long posts used to hold the nets in place.

In addition, Groll said: ''We have pictures of small white objects. We don't know if they're animals or fungus; they may be geologic in origin. We don't know what it is.''

Apart from the gill net posts, the only other man-made objects sighted during the morning dives were ''lots of bottles and beer cans,'' Groll said.

The Sea-Link II is equipped with cameras to make videotape recordings of the lake bottom as well as color slides, Long said. Between 700 and 1,400 slides would be made during each dive, he said.

The submarine's batteries allow it to operate for three to four hours, but then require about three hours to recharge, Long said.

Groll said the 22-foot submarine was ''pretty comfortable.

''It's quite warm; there's not much leg room ... (but) there's plenty of elbow room, plenty of operating space,'' he said.

The expedition was to remain in Whitefish Bay in extreme southeastern Lake Superior through Wednesday, Long said. It will then head northwest and due west for the next phase of the expedition, ending July 31. Two more phases are to begin in August.

Divers have reached the bottom of southern Lake Michigan near Chicago and have found sunken ships in other parts of the lakes, but this expedition is believed to be the most extensive of its kind, Long said.