PrimedTnt is able to me moved by water currents. i first found this bug in 14w28b it still exists in 14w30c.
Linked issues
is duplicated by 1
Comments 2
This is intended behavior as far as I know. Primed TNT is supposed to be affected by gravity and water.
MC-665 is not a duplicate, it is "related" only.
WAI. MC-665