The undersea effort was prompted by a claim from a volunteer searcher that his radar, Cobiella says.
On land, the probe of Holloway's disappearance some three months ago resulted in round two for Surinamese brothers Deepak and Satish Kalpoe, who were questioned for several hours Saturday, and again on Sunday.
Prosecutors claim they have new evidence against them, and arrested them on suspicion of rape and murder early Friday morning. They'd been held earlier in the investigation.
One of their attorneys says he's seen nothing.
"They haven't shown us any evidence," asserts Elgin Zeppenveldt, a lawyer for Satish.
Asked if that's normal, he responded, "No, it is not normal. Only in Aruba is it normal."
A fourth man also has entered the picture, Cobiella says.
Freddy Zedan Arambatzis, a close friend of Joran van der Sloot's, was also arrested Friday. He calls himself "Locoman Pimp" on his Web page, and is a familiar face in pictures of van der Sloot and the Kalpoes.
Van der Sloot had been the only suspect being detained in the case until the latest arrests of the Kalpoe brothers.
However, prosecutors aren't saying whether Arambatzis is being held in connection with the Holloway investigation.
Holloway's mother, Beth Twitty, and stepfather, George "Jug" Twitty, heard about the arrests while at home in Birmingham, Ala.
"Beth and I are very, very happy because that's what we wanted and, I mean, they have, they have some answers," he says.
"And you know Jug and I and several other family members, we felt early on, as early as May 31, that these boys (the Kalpoes) should have, should have been arrested then on that day," she added.
Meanwhile, the legal clock is ticking for van der Sloot, Cobiella says. He could be released as early as this week.
Prosecutors have until Sunday to either charge him or persuade a judge to hold him for another 30 days.