Making an underwater campaign as a first time dm /u/Lonely-Kitchen1951 DnD: Roll for Initiative!

Okay so I’ve only played DnD for a year with my friends with Icewind Dale. I wanted to make my campaign about solving a problem underwater to stop the world from flooding as each year the tides has only gotten higher making people fight for land. I don’t know if there is a prewritten story that’s underwater based? So I’m making a homebrew campaign. I know prewritten stories are best for first time DMs. I asked my friends about making my own and they basically said not to make it so complicated and have fun with it. Like be chill with it. But when I compare it to my last campaign I played I felt like there was so much to the story and my friend did a great job telling it through the adventure. So I’m trying to come up with a story that’s just as cool and makes sense or at least try to. I’m not that worried about the rules. I’m more worried about the details and making sure it runs smoothly. But I also don’t want to overthink either. Like there should be a reason why the world is flooding because of so and so and little details that foreshadow what’s to come. That and I thought it’d be nice to add in a few underwater kingdoms along with the world being fairytale but there’s machines and stuff like a submarine and underwater suits. I guess I just want other opinions to see if I can put it together okay or should I go with a prewritten story I already have??

Okay so I’ve only played DnD for a year with my friends with Icewind Dale. I wanted to make my campaign about solving a problem underwater to stop the world from flooding as each year the tides has only gotten higher making people fight for land. I don’t know if there is a prewritten story that’s underwater based? So I’m making a homebrew campaign. I know prewritten stories are best for first time DMs. I asked my friends about making my own and they basically said not to make it so complicated and have fun with it. Like be chill with it. But when I compare it to my last campaign I played I felt like there was so much to the story and my friend did a great job telling it through the adventure. So I’m trying to come up with a story that’s just as cool and makes sense or at least try to. I’m not that worried about the rules. I’m more worried about the details and making sure it runs smoothly. But I also don’t want to overthink either. Like there should be a reason why the world is flooding because of so and so and little details that foreshadow what’s to come. That and I thought it’d be nice to add in a few underwater kingdoms along with the world being fairytale but there’s machines and stuff like a submarine and underwater suits. I guess I just want other opinions to see if I can put it together okay or should I go with a prewritten story I already have??