Are those blue spaces on JLA Watchtower map water spaces?

You must mean the pool and the hot tub. Yes.

Is the JLA table on the map all hindering terrain? What if a fig is standing in middle square of table? Is that hindering terrain?

Another question: If your in hindering terrain with more than a 4 square area, such as a table or truck, and you want to move from one end to another, can you move freely there, move at half speed, or stop because you're entering another hindering terrain square? What are the rules for moving inside hindering square area?

Last I heard from DrGandalf the table was all hindering terrain as it was one feature outlined with a thin line. The map FAQ is supposed to be on its way.

As for the second question, you only stop when entering hindering terrain from non-hindering terrain. Moving through hindering terrain can be done without stopping but at half speed.