1. what kinds of factors could hinder the forward progress of a message in a bottle in an ocean current? what factors could aid the movement?

1)  The main factor that could hinder the forward progress of a message in a bottle in an ocean current is "Great Pacific Garbage Patch." which size is similar to one of Texas. It is a gyre of marine debris particles that contains a huge amount of pelagic plastics, chemical sludge and other debris that currents usually bring.
2) The factor which could aid the movement is the force of a current which would take the bottle and the path of the current that flows in the right direction.According to the statistics of related investigations, this factor seems to be the only one that could could positively aid the movement.

Ones bigger then than the other