What is the opposite of across in prepositions?

As a preposition, across can be used in many ways. Some examples of opposites in use:

We can get to the other side across the lake or around the lake.

We can travel to Spain sailing across the ocean or flying over the ocean.

We will make it across the chasm or fall into the chasm.

You may use the phone across the room or up the stairs.

We can travel across the country or stay athome.

We will make it across the border or land injail.