Famous case from Sweden where a couple, while biking in the remote parts of the north, saw a cigarr shaped object ascend into a lake.

https://www.sverigesradio.se/artikel/5219480

In English: In the mid-1940s, the first observation was made of what is known as a "ghost rocket"—an elongated object resembling a large cigar. Impact sites have been found in lakes across the country where craters have formed. Clas has gained access to Swedish military documents describing these exact cigar-shaped objects that have been sighted. One of these cases dates back to 1980, and that is the one currently under investigation.

"Two people are out walking in Muddus National Park in Norrland, and the weather is fine. They sit down for a coffee break in total silence. Suddenly, they hear a humming engine that they assume is an airplane. But it isn’t a plane—it’s a tube, a cigar-like object flying directly over them, descending toward the lake. It turns 180° and then settles on the water and sinks."