Meteorology may also play a part.
This accident happened near the Cornish coast and the film of the crash site clearly showed IMC weather conditions.
But, I was speaking to a non-pilot, who surfs around Cornwall, and he said that, at times, the sea mist can roll in very quickly and unexpectedly catching out sailors, surfers and even people on the beach, who lose site of their kids - one minute it's bright and sunny, the next it's grey and gloomy.
What are the tell tale signs to look out for?