What Happened to Mars' Ocean? It's Still Trapped There

So, Mars used to be this cool planet with an ocean, believe it or not. But that ocean is now kind of stuck, nowhere to go. Scientists think it turned into ice and got trapped under the planet's surface. Imagine having an ocean but being unable to take a dip! They reckon the Red Planet's climate change played a part in this aquatic lockdown. So, long story short, Mars' ocean is still hanging out, just in a frozen, underground state. Talk about a cosmic chill, right?