http://www.googleartproject.com/museums/uffizi/hercules-and-the-hydra-and-hercules-and-anteo-61
This is a very mysterious piece with not much information to be found on it. It was created by an artist named Antonio Del Pollaiuolo. He was born in Florence Italy, and began working on his artistic qualities very early on with his brother. He found his greatest success as a metal worker and a sculptor. The piece that is listed above was created in the year 1475 and is one of his most famous pieces, but that is the extent of what is known about the painting. I chose this piece due to deep interest in mythology and my familiarity with this particular story. I took an ancient mythology class here at Florida State and had to analyze the story of the hero Greek hero Hercules. I greatly enjoyed the story and I believe the painting is merely a visual representation of Hercules’ battle with the fearsome Hydra. The painting shows Hercules wearing little clothing which may represent his mortality. He is wearing a lion hide on his head which represents his previous conquest of the Nemean lion. Hercules is shown grasping the middle head of the Hydra signifying a near end to the battle as his club is drawn.
Britannica
compresearch1102 
I found the painting to be interesting as well, as the story of Hercules and Hydra has always intrigued me. I find it weird though that Hydra in this case is smaller than Hercules. I do not know if this is because I watched the cartoon movie that I am getting this misconception. I have got to disagree with you in regards to the lack of clothes. This may be showing his immortality more so. He is fighting hydra with no armor, and stands as a giant on the earth, unless this is portrayed on a hill or something like that.
Andrew Morton