What are advantages and disadvantages of water transport?

Advantages:

1. Cheapest traffic means
2. Most important in security of nation
3. Plays important role in international trade.
4. Possesses high load carrying capacity.
5. Requires cheap motor powers than for airplanes.
6. Does not require any special infrastructure like roads, and airports.
7. Brings many countries together.

Drawbacks:

1. Slow in speed
2. More chances of attack on boat sailing through
3. Only can be used when sufficient water is available.
4. In deep sea if boat gets in to storm, it becomes difficult to rescue.
5. In waterfalls having much drafts ,water transportation does not works.
6. Special maintenance for water tightness of boat is required.