Here are my observation on Marinecoin:

• Devs hold the whole lot (almost all) of premined coins.
  
• If you check the explorer, the top few holder hold more than ninety percent of them.
      https://explorer.marinecoin.info/richlist
  
• It is listed in their in-house exchange without any buy orders. It is risky to trust them and end btc there as there is no specific term of the exchange mentioned on the site.
  
• There is no guarantee that the dev will not sell their own coins and move on.