Swimming

"Swimming" often describes handling groups that don't have a base. The base is the potential to make two eyes (this is easy in the corner or on the sides). Groups that don't have a base (no potential to make eyes in the corner or on the side) will have to swim, towards the center, because the side is already taken by the opponents pieces that remove our potential to make eyes there.

"Floating" is related and describes groups that dont have a base. "Swimming" is the act of taking care of a "floating" group. This nice metaphor is often used by badukdoctor ;)