"Submergence" - story idea, TOS or TNG eras
The world is 90% water, though it was once 60% water, due to adverse climate change 400 years before the sea level rose and the populace was forced to the worlds mountain ranges. The planets population was reduced from 12 Billion to the current 4 million.
20 years ago the worlds government pressured by a slowly growing population and lack of suitable farm land started a program to lower the water level through the creation of gigantic underground water aquifers spread over the planet's Sub-surface, essentially moving the water underground. Though the world has not joined the Federation, it has been asking for over 70 years, it asked for technical assistance to do this.
The Federation accepted the request and for 10 years a Federation scientific research team has been working to help achieve the worlds goals. But not all the worlds citizens support this goal nor the fact of Federation assistance on planet or the goal of joining the Federation.
Now with the time of the first aquifer going on line near the end of the month the government is a afraid of sabotage in an effort to stop it. No longer completely trusting their own security force the government has asked for a Starfleet to be dispatch to ensure all goes well.