Is this a bad apple?
This appears to be watercore, specifically radial watercore, from the image you have posted.  It should be safe to eat, according to this site and this site.

According to an article from Washington State University, watercore is a disorder of some apple variants, which can cause the internal flesh to appear glassy [shiny and translucent] later into the growing season.  In some studies, low levels of calcium have been shown alongside the condition.  As well, it should be noted that the condition 1) does not occur after harvesting 2) may cause an increase of sweetness, and 3) cause the apple to quickly degrade during storage.

As to the causes of this disorder, there are a number of theoretical factors for causation:  Genetic defects, water regiment, temperature, minerals, leaf-to-fruit ratio, maturation and ripening, sorbitol metabolism and altered transport.  These are discussed to some degree in both the WSU article and this MSU article