They can safely fly within a few inches of water.
That's what they are good at.
They don't. That pic is a fake, a montage.
The air is too thin at 29,000 feet for helicopters to fly. That is why, when a mountain climber is sick or injured, he must be carried down to a base camp low enough for a helicopter to evacuate him.
I think you are thinking of the Russian Ekranoplan, which uses a 'Wing in ground effect' to travel very fast, low over water.
I have found nothing in any search to support that a boombox can drown out a low-flying airplane or helicopter.
I've never heard that. However, helicopters are limited to the altitude that they can hover, which would limit a Rescue helicopter from picking up a stranded mountain climber. In the high altitude, the air is "thinner" which means the air pressure is less. This limits the effiency of the rotor blades. However, usually the first indication of a problem is when a helicopter tries to hover at high altitude and the tail rotor looses it thurst and the helicopter goes into an uncontrolled spin. This was common with the Bell Model 206B. Even though a helicopter may be limited to the altitude at which it can hover, that does not mean it can't fly at that altitude. If a helicopter maintains a high forward air speed, it can still fly over mountains; its only when it stops and hovers that it may have problems.
Bees can fly up to 55,000 meters in a two week period. If the ocean is on low tide, they generally do fly over. Eventually dying several miles at sea.
with skill as low as a few inches off the ground
The Canoeist is halfway between Fireworks Launching Area 1 and Wedge Island. Start at the fireworks point and fly low over the water until you see the "i" hovering over it.
Most RC mode-3 instances of overuse (letting the voltage drop too low) they will not charge adequately.
The low side is about 25000 mph, the upper limit is over 100000 mph.
A spy helicopter main job is to spy in enemy bases in low places and some times it can send troops in there