The search continued Sunday for a 13-year-old boy missing in Lake Lanier since Monday night when the pontoon boat his dad was driving was hit by another boat in a collision that killed the teen's 9-year-old brother.

State Department of Natural Resources divers were focusing on an area of the lake where sonar equipment detected what potentially could be the body of the missing 13-year-old. The FBI will bring in equipment Monday that will allow divers to stay under water for more than six minutes at a time in an effort to complete their search, authorities told Channel 2 Action News.

Meanwhile, seven people were arrested on boating under the influence charges -- five on Saturday evening and two on Sunday -- during a weekend-long sweep for boaters driving drunk or violating other regulations as part of Operation Dry Water.  According to Sgt. Mike Burgamy, the agency averages about three arrests on a typical weekend.  "We are aggressively enforcing it this weekend. I have a little extra manpower, so that helps."

The crackdown had been planned before last Monday's boating tragedy that killed the two boys as their family enjoyed a late-night cruise. The collision occurred at one of the deepest areas of the lake near Buford Dam.

Jake Prince, 9, died of massive injuries and his brother Griffin, 13, was thrown into the dark waters. Paul J. Bennett, 44, the man who allegedly piloted the speeding 21-foot boat that hit them, has been charged with boating under the influence and could face charges of homicide by vessel.

Boaters interviewed by Channel 2 said the brothers' deaths were on their minds as they launched their crafts Saturday and Sunday. As morning temperatures rose in the first weekend of summer, the lake grew crowded.

Supporters held a vigil for the family Sunday. The siblings' step-grandmother, Deneice Prince, told The Atlanta Journal-Constitution that the family is delaying any memorial service until the 13-year-old is located.

"(We'll be) back to full operations tomorrow with all the agencies and other resources coming in to see if we can bring closure for the family," DNR Sgt. Lee Brown told Channel 2.

Staff writer James Salzer contributed to this report.