A bizarre UFO-like funnel cloud formed after a waterspout was spotted off the coast of Thailand.

The twister rotated on choppy seas as dark clouds hovered in Chanthaburi province on May 6.

But when it was gone, an unusual swirling tornado-shaped cloud was seen in the sky, alarming the tourists.

Footage shows the waterspout off the coast, followed by the funnel-shaped formation.

Holidaymaker Phongphot Pankham said: ‘It looked like an alien UFO. It also looked like an elephant trunk. It was so big and a bit scary.'

A heavy downpour followed the unusual formations.

Waterspout tornadoes form when wind merges from opposite directions near the water's surface, creating a small area of spin. Warm air at the surface causes the spinning air to rotate faster and it starts to rise – picking up water at the same time and forming the distinctive elephant-funnel shape.

As warm air rises, the cooler air moves in below and then rises, too. Sometimes the air spins so fast that it stretches and a funnel appears from the water to the thunderstorm cloud above.

Waterspouts are generally not dangerous but they can be a risk for aircraft flying through the area and for coral reefs and marine life in the water immediately below. Sailors should also try to avoid waterspouts as the power of the wind can cause damage.

They very rarely damage buildings as they dissipate when they reach land. However, they are dangerous of boats caught in their path or aircraft that fly through them.

On the other hand, funnel clouds are cone-shaped clouds that extend from the base of the clouds towards the ground but does not touch the surface.