- Pontoon bridge (Wikipedia)
A pontoon bridge (or ponton bridge), also known as a floating bridge, uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maximum load that they can carry.
- Siege of Tyre (332 BC) (Wikipedia)
The siege of Tyre was orchestrated by Alexander the Great in 332 BC during his campaigns against the Persians. The Macedonian army was unable to capture the city, which was a strategic coastal base on the Mediterranean Sea, through conventional means because it was on an island and had walls right up to the sea. Alexander responded to this problem by first blockading and besieging Tyre for seven months, and then by building a causeway and placing siege towers with catapults built on top at the end after his soldiers discovered that they could not extend it any further due to a steep drop under the surface of the water. This allowed him to breach the fortifications.