Thank you very much, Shax.

A current is the force that pulls and pushes you along in flowing water, so when this force pulls or pushes you fast, it is called a 'swift current'. 'Imposing' is the action of giving, that is done by someone, to someone else. If I gave you a fine, I 'imposed' it on you. If I gave you a deadline, I 'imposed' it on you. If something carries a fine, it means that you will be fined if you do that action. For example, if the action of parking in front of a store carries a fine, then you would b fined if you parked in front of a store. So the last 3 phrases are about the same subject, but do not mean the same thing.