Before, a boat fully or partially submerged in a waterfall would rise upwards.

Since updating to 1.4.6 the waterfall will push the boat downwards through any blocks below. The boat will have a hit-box in it's "glitched" position, however touching the hit-box in it's "true" position will cause it to return briefly to it's "true" position before glitching back through the blocks below. The boat only seems to fall about 6 blocks below it's starting position, even if there are no other blocks below it's "new" position, causing it to flat in the air - the hit-box is still active in it's "new" position. Disrupting the water flow will sometimes, but not always seem to return the boat to it's "true" position. Sometimes the boat will become invisible and not return to it's true position leaving an invisible and irremovable hit-box where the boat should be.

Same effect in both creative and survival.

Steps to Reproduce:
Place a boat on a block and let a water stream fall past the side of the boat, such that part of the boat intersects the water stream.