On December 10, 2000, at about 1903 eastern standard time, a Robinson R22, N411MJ, registered to Fourth Millennium Enterprises Inc., operated by Volar Helicopters Inc., as a 14 CFR Part 91 instructional flight crashed into the Atlantic Ocean about 100 yards offshore of Marathon, Florida. The pilot reported instrument meteorological conditions, and no flight plan was filed. The helicopter was destroyed. The commercial pilot flight instructor (CFI) and student pilot reported minor injuries. The flight originated from Indian Key Island about 18 minutes before the accident. The CFI stated he departed Key West, Florida, at about 1530, following another Robinson R44 helicopter. No weather briefing was obtained before departing on the VFR flight to Fort Lauderdale Executive Airport. He was southwest of Islamora, Florida, when they encountered instrument flight conditions due to reduced visibility from rain showers. He lost sight of the R44 and made a 360-degree turn for spacing and notified the other pilot of his actions. He then continued flying up highway US 1 until he realized he was going to lose total visibility. He made a left 180-degree turn towards clear skies before turning back to the east, while the R44 pilot landed. He observed Indian Key Island, flew out to it and landed at about 1630, with the intentions of waiting the weather out. He called Miami Automated Flight Service Station and received a standard weather briefing at about 1743. The forecaster informed him that VFR flight was not recommended due to a line of thunderstorms being present along his planned route of flight and a convective sigmet that was current. He called his employer a short time later and informed him that he had made an off site landing due to weather. His employer told him not to take any chances and to remain there over night if necessary. The weather improved and he departed the island at about 1845. He flew over to US 1 and encountered instrument conditions. He reversed his course towards Indian Key Island, lost directional control of the helicopter due to spatial disorientation and the helicopter collided with the ocean.