So there are these 2 games, I can't tell you enough how much it bothers me that I can't remember the names, I used to play them as a kid in the late 90's/early 00's...
1) and undersea point and click adventure for the pc, possibly a learning game, where you would go from screen to screen, solving problems, there was Poseidon and his trident, and I remember you were looking for these sea urchins as a bonus once and a while. I'm pretty sure the person you guided was a diver, the game was dark, and well drawn from what I can remember, and the cd case was possibly part of a set of adventures related
2)a weird and creepy pc adventure/mini-game from the 90's/early 00's where you crawled through vents and looked down into rooms, I don't remember the point of the game, all I remember was that there was one mini game where you could play squares with a hand that would draw a line between dots on the foggy window after you made your move, it was another dark themed game for parts, and I wouldn't know what the full objective of the game was