His solution has been to work with lines alone - usually using two colors - and keep them on the surface.

At some speed, the Earth's gravitational force would not be enough to keep us on the surface.

This allows them to keep their correct position on the surface, ready to resume play once they have recovered.

He'd be all right so long as he kept everything on the surface, though.

With the main periscope out of action, he kept the boat on the surface.

Only it was worse then, maybe, since no one really cared, so long as things were kept quiet and decent on the surface.

There was very little gravity to keep them on the surface, but the suits were able to compensate.

They all learned pretty early, though, to keep their eyes on the ones in front of them and on the surface itself.

As a result, he wanted to keep things on the surface.

So your first order of business is to find out what keeps it on the surface.