The Star Block is a special block in Build A Boat For Treasure. It first debuted on June 12th, 2018 at 3:30 Central Time. It appears to glow when in 2 graphics quality but only has a very dim glow, unnoticeable in broad daylight. It has nothing to do with the free star save. Painting the star block will cause it to glow the color of the paint. This was added due to the game having 1 million Favorites. Ten star blocks are given for free when joining the game during the 1M Favorite event. This is one of the only 2 blocks that glow, the other being the Neon Block.
You can redeem the code "ow" for 20 star blocks or "Gnomed" for 10.