I too came up with 12 feet.
1/3 is in the water and 8 feet is out of the water.
8 feet = 2/3
1/2 of that is 4 feet
So each 1/3 is 4 feet
It doesn't matter how much is in the ground as long as you know how much is in and out of the water.
I see in your calculations where you've accounted for the 1/3 of the length that is in the water and the remaining 2/3 that are not in the ground. Where is the portion that is in the ground?
In US english, when you say something is "out of the water," it means that it is completely out of the lake or whatever body of water it is, and the space below it is not considered to be "out of the water." Also, when stated as: "One half of the pole is in the ground," it is understood to mean: "One half of the total length of the pole is in the ground." The second part of the statement, directly following the first part says, "another one third is covered by water " which is understood to mean "another one third of the total length of the pole is covered by water," however, the "of the total length of the pole" is not repeated because it is simply understood. Unless the OP specifies or clarifies, I think the answer should be 48.
What is not clear is if the pole is straight or if it changes shape like lost in space mentioned, a pole that bends
One half of the pole, (3/6ths) is in the ground.
Another one third of the pole, (2/6ths) is in the water, leaving only 1/6th remaining.
8 feet, our remaining 1/6th of the total length of the pole, is out of the water.
So if 8 feet is 1/6th of the pole, the total length of the pole is 8*6=48 feet.