The U.S. Navy is playing games on Reddit in an attempt to draw in recruits for submarine crews. At the end of September, the U.S. Navy launched its new “Sub Reddit Hunt” a campaign on the social media site. Throughout the month of September, the Navy will “hide” five submarines on Reddit and leave clues that potential recruits can use to track down the submarines.

The game is an advertisement meant to drum up recruitment. It’s the brainchild of VML, an advertising agency that’s worked with Microsoft, Coca-Cola, and Ford. “This interactive marketing campaign encourages Reddit users to decipher codes and search for clues to complete command directives—designed to attract the next generation of submariners,” Marketing agency VML said in a post on Facebook announcing the campaign.

The U.S. Navy, and most other branches of the U.S. military, are having a hard time getting people to enlist. Over the past decade, the Army, Navy, and Air Force have struggled to meet their recruitment goals. The Navy is one of the worst performers and has failed to recruit sailors consistently over the last few years.

The reasons why are complicated. Decades of unpopular foreign wars have tarnished the reputation of the military. A good economy means more jobs, which means that fewer young people are pushed into enlisting for a paycheck. Many branches also won’t let people join if they’ve ever used an illicit substance like marijuana, have a tattoo, or have used psychiatric meds. Americans are also more unhealthy than they’ve been in generations and can’t meet the basic physical requirements.

All of that adds up to fewer people joining the military. All the branches have gotten creative in the last decade as they’ve tried to drum up recruits. The U.S. Navy and Army both maintain active esports teams, stream on Twitch and Facebook, and attempt to use video games to drive recruitment. It hasn’t always gone well.

The Navy, and other branches, were already advertising on Reddit. The augmented reality game is just an evolution of that tactic. “To ensure we attract the very best and brightest future sailors, including submariners, the Navy is constantly seeking innovative ways to interact with prospective candidates on … social and digital platforms,” Rear Admiral James P. Waters, commander of Navy Recruiting Command, told AdAge in a statement.

The Navy has released two of the games and will release more as the month rolls along. The first is a long list of redacted statements that users click to clear away. Underneath the bars are clues that could help interested recruits track down the first hidden sub.

The second game is an audio puzzle. Clicking an animated gif sends users to a Google drive where the Navy has uploaded 8 different audio files that, if deciphered, will lead them to another sub. Gizmodo ran the audio files by a former U.S. Navy sonar tech who told them they were a mix of things someone might hear.

One contained morse code, another sounded like bridge chatter, and another sounded like a repeated string of Chinese. The former sailor said the audio was old fashioned. “We rarely actually listened to the noises. We mostly just look at the displays of the sounds, you get a waterfall display,” he said. The sailor didn’t work on a sub, however, and added that “sub-based sonar techs might listen more than we did. Surely they do.”

The last puzzle is set to go live on October 28. According to a statement from VML, the puzzles “[ask] Redditors to go deeper than ever before to solve a problem and learn about the Navy.” It’s unclear if the strategy will work.

Navy Recruiting Command did not immediately return Gizmodo’s request for comment.