Strange shape observed gliding over Galveston island during a warm Saturday afternoon.The object we saw was elongated with a larger bulb shaped front. It was a light grey and moving slowly (gliding) across the sky. It slowly moved about the length of a football field (I'm not good at guessing aerial distance) into some clouds and out of sight. The object could be seen for about 20 seconds. This occurred during a warm sunny day with some clouds and haze. The shape and it's movement could be seen very clearly as we approved the causeway connecting Galveston island to the mainland. There had been an airshow during the day, however this craft did not have visible wings nor did it appear to be a vintage aircraft like those in the airshow. I could not see any lights or markings of any kind.