How foolish is it to say that the Aliens live underwater and in tunnels of mountains since 1000s of years?

Extremely foolish as there's the question of why would they go to so much trouble even to visit our planet let alone the immense improbability of even knowing we exist.

The History and Discovery channels are ultimately commercial ventures and will do whatever will bring them money in their market niche. I thoroughly expect them to someday rebroadcast certain sci-fi shows that have cult followings but were canceled by other networks. It's like how MTV is not the MTV it began as.

Like I said before - very foolish. History & Discovery channels will stop producing those dumb shows when people stop watching them...

Very foolish. There is absolutely no scientifically acceptable evidence that any extraterrestrial has ever visited Earth.

Any claim without any proof or evidence to support it is foolish.

Doesn't matter if is aliens or angels or Bigfoot.

Without any evidence, it is very foolish.

who says they travelled here ? maybe they were here first and advanced so much that they left long before america was discovered,did humans not once dwell in caves ?evolution my dear friend