**SPOILERS*** The Water Puzzle SPOILERS -
In FINAL MISSION, Picard, Wesley Crusher, and some idiot miner named Dirgo, crash land on a desert moon. The moon is uninhabited. They walk across a desert because Wes picks up an 'energy source' on his tri- corder. When they get to some caves, the three of them, now nearly dying of thirst from the heat and lack of water, find what amounts to a large drinking fountain. But of course, it's protected by a 'force-field' - which when Dirgo insists on continually firing phasers at, kills him, and ensuing rock-slide critically injures Picard.
Wesley, as usual, comes up with some 'techno-babble' way to deactivate the force-field, thereby saving himself and an injured Picard until the Enterprise eventually finds and rescues them (for most of the episode, they've been dealing with a radioactive garbage scowl that's threatening to poison a planet - so we get a nice little environmental message here as well).
Question: Why does this fountain have a force-field around it? It's a deserted moon, no life, no sign of life, except for a big protected drinking fountain. Why would anyone put that there??? Who did put it there???? Even if it was put there by someone else to have a safe water supply, it begs the question - if they left that moon, and planned to return (therefore they have space travel ability) why not just bring water with you when you return?? Also, the amount of water coming from this fountain would indicated a huge underground water source - on a desert moon. The entire concept is absurd. And why wouldn't they just use their phasers a few feet way to dig another path to this underground water source? Why play games with this absurd force-field, that for some reason, has already killed one person?
The problem here is, it was created by the writers as a plot device to give Wes something to do, be the hero, and stretch out the story.
Usually TNG explains things like this. But here, they all just shrug their shoulders, beam everyone up to the ship and fly away. STUPID.