When you have the Invisible condition, you experience the following effects.
Surprise. If you're Invisible when you roll Initiative, you have Advantage on the roll.
Concealed. You aren't affected by any effect that requires its target to be seen unless the effect's creator can somehow see you. Any equipment you are wearing or carrying is also concealed.
Attacks Affected. Attack rolls against you have Disadvantage, and your attack rolls have Advantage. If a creature can somehow see you, you don't gain this benefit against that creature.
The condition expressly contemplates a situation where a creature could 'somehow see you'
You could be hidden (and thus have the invisible condition) at the start of your turn via hiding inside a sarcophagus (and out of sight of an enemy).
The enemy - on their turn - could then walk up to the sarcophagus and simply look down and in, and they would now be able to see you (the thing making you 'invisible' to them was self evidently the sarcophagus walls).
You then lose the invisible condition that was granted to you from hiding (you expressly lose it if a creature 'finds you').
To me, that just seems the common sense interpretation of the rules.
That said, if people want to run it as 'you duck into the sarcophagus in full view of the enemy, take the Hide action and hit the Stealth button, roll a 15+ and you're suddenly translucent, even if the enemy creature literally walks over and looks down into the sarcophagus where you're lying' then by all means, go for it.