https://www.reddit.com/r/WritingPrompts/comments/j8jtx4/wp_humanity_has_been_driven_into_the_sea_by_the/ Humanity has been driven into the sea by the undead. 100 years later the boats and ships are sinking...
Undead
https://www.reddit.com/r/WritingPrompts/comments/j6g2ah/wp_the_hellish_trenches_of_the_great_war_were_dug/ This only took three tries to get something coherent and relevant to the topic that was good enough quality...