While surfing in Hawaii, Marcus was thrown by a huge wave that caused his surfboard to hit his head, causing him to temporarily lose consciousness and almost drown. After being revived by a fellow surfer, Marcus reported seeing a light in a tunnel that he felt impelled to enter. This experience can be explained as being caused by:

Oxygen deprivation to the brain

Explanation:

The brain is regarded as the most important part of the body, because its activity controls all other parts. It is known to be the part the make use of the highest amount of oxygen in the body, this is because of its many activities.

It should be understood that, whenever there is oxygen deprivation to the brain, all other parts will be affected. This is because, as said earlier, it is that part that controls all other parts in the body.

It should be noted also, that the damage caused to the brain will depend on the extent of the oxygen deprivation. And some people can recover with little or no consequence, while in some it may be fatal.

In this case, Marcus was seen another which was different from what he supposed to be seen because his brain was shutting down due to oxygen deprivation, and would have been fatal or resulted to death if he has not been rescued.

Answer: Oxygen deprivation to the brain

Explanation:

Oxygen deprivation could be described as when there is limited oxygen presence in the brain or when oxygen doesn't reach the brain. This could be noticed by the following symptoms; suffocating, stroke, drowning, cardiac arrest, memory loss and severe cases seizure which can cause death. After Marcus hit his head he experienced a lack of oxygen in his brain, leading to loss of consciousness and almost getting drowned.