Collin County deputy, scuba instructor arrested after 12-year-old drowns at Scuba Ranch

William “Bill” Armstrong, a former Collin County assistant chief deputy who worked as a NAUI-certified scuba instructor, was arrested Feb. 6 and booked into the Kaufman County jail on a felony charge of injury to a child in the drowning of 12‑year‑old Dylan Harrison. Armstrong posted $150,000 bond and was released the same day.

The drowning occurred during an open-water certification class at The Scuba Ranch in Terrell on Aug. 16, 2025. The family’s complaint and local reporting say the class entered the water at 9:36 a.m. and the group resurfaced at 10:12 a.m.; Dylan was not accounted for when the group came up. Emergency crews were reported to have arrived around 10:30 a.m. Her body was later recovered approximately 45 feet deep and about 35 feet from the training platform.

Heather and Mitchell Harrison filed a civil lawsuit on Jan. 30 alleging negligence and safety failures by instructors and the dive operation. The complaint alleges Armstrong did not check whether Dylan was properly weighted before entering the water and that he had worked consecutive long shifts the day before the class, including a full day as a deputy followed by an overnight security shift, leaving him with “little or no sleep in the past 24 hours.” Those shift and fatigue claims are presented in the lawsuit as allegations. Witness affidavits cited by the family’s attorney say Armstrong was “bone dry” on the platform when other divers began searching for Dylan.

The suit includes detailed assertions about Dylan’s air supply. As quoted in reporting of the complaint: “Based on the amount of air left in [Dylan’s] scuba tank on the surface before she went missing and the amount of air left in the tank when she was found, it can be surmised that [she] was alive and breathing off her tank for several minutes after she was last seen... During this time, [Dylan] was alone, in poor visibility, and unable to reach the surface.” The family’s attorneys also say crucial dive-computer data was not collected and that one dive computer is now missing.

Eight students, an instructor and a divemaster were on the class roster, and the divemaster is quoted in the lawsuit as telling the family, “I will not take my eyes off your daughter.” The Scuba Ranch has said it was “heartbroken” and has permanently suspended Armstrong from teaching classes. Armstrong resigned from the Collin County Sheriff’s Office in October following the incident.

Plaintiffs further cite a 2017 video involving Scubatoys owner Joseph Johnson in which he allegedly said, “All I know is we've killed, what, 4 people, 5 people, and we've never even done a deposition,” and “Our insurance company just settles.” Those statements are presented by the family to underscore alleged systemic safety problems in training operations.

For Collin County residents, the case touches on public safety and regulatory oversight of recreational dive instruction, protocols for supervising children in water-based certification classes, and how worker schedules and multiple jobs may affect instructor readiness. The criminal charge against Armstrong and the pending civil suit leave many questions unanswered; official records such as the police incident report, 911 call logs, dive-computer files and the medical examiner’s report will be critical to establishing timelines and responsibility.

The arrest advances the criminal process, but court dates and formal filings have not yet resolved the factual disputes in the lawsuit. Families and community leaders in Collin County now face decisions about local oversight, training standards and transparency from dive operators as the legal cases proceed and investigators compile evidence.