Near-death experiences have been extensively studied by scientists, and there are many examples online of their research and findings.

They seem to conclude that such phenomena are due to physical causes such as anoxia, too much carbon dioxide, hallucinations produced by opiates such as diamorphine, and other physical brain disturbances.

It's interesting that most NDEs are similar ('light at end of tunnel', visions, voices, sensation of floating etc) which suggest to me they are phenomena associated with unusual brain activity (or lack of)

I can truly say I 'believe' in an afterlife, but there is no way I can prove it. And I would never try to assert such a belief forcefully to anyone.