Complex sentence: That diver was concerned of landing on unauthorized swimmers in the pool, which he claims was a frequent occurrence in that era; the area was list as barricaded in an early report, but later reports contradicted that.
Split into simpler sentences: That diver was concerned about landing on unauthorized swimmers in the pool, which he claimed was a frequent occurrence at that time. The area was listed as barricaded in an early report, but later reports contradicted that.