What are the signs and symptoms of hyper hydration?

Answer 1

Lethargy, confusion, agitation, and possibly seizures - the problem is that when you drink too much water, you decrease the amount of sodium in your blood, and sodium is needed for muscle movement.

Here's what a couple of expert doctors have to say (link below):

As these symptoms may mimic frank dehydration, some athletes mistakenly conclude that plain bottled or tap water may be the most desirable approach to rehydration. Nothing could be further from the truth-too much fluid can hurt!
Hyperhydration, which contributes to hyponatremia, is an emerging concern among trainers and health care professionals and a condition that can be prevented. Adequate consumption of properly formulated and clinically tested electrolyte-containing beverages as part of a fluid-replacement regime during exercise and endurance events can prevent or reduce the risk of hyponatremia and related sequelae, while maintaining fluid balance and important physiological functions