It explicitly says they were not picking up the recorded object in that linked Wikipedia article.
"When the jet fighters arrived on site, the crew of four saw nothing in the air nor on their radar"
So there's some mysterious radar pickup on the boats but the pilots then chase their own shadow and record it.
The real kicker is this part
"As Fravor further descended, he reported that the object began ascending along a curved path, maintaining some distance from the F-18, mirroring its trajectory in opposite circles. Fravor then made a more aggressive maneuver, plunging his fighter to aim below the object, but at this point the UFO accelerated and went out of sight in less than two seconds, leaving the pilots "pretty weirded out"."
"When the jet fighters arrived on site, the crew of four saw nothing in the air nor on their radar"
So there's some mysterious radar pickup on the boats but the pilots then chase their own shadow and record it.
The real kicker is this part
"As Fravor further descended, he reported that the object began ascending along a curved path, maintaining some distance from the F-18, mirroring its trajectory in opposite circles. Fravor then made a more aggressive maneuver, plunging his fighter to aim below the object, but at this point the UFO accelerated and went out of sight in less than two seconds, leaving the pilots "pretty weirded out"."
That's a literal shadow!