A Brief History of the Amphicar – President Lyndon Johnson’s Favorite Car (2020)

San Francisco may have a harbor and bridges, but it's hard to drive right into the water. After 911 they added balusters to prevent vehicles from leaving the roads, so you would not be able to access the water near a bridge from a car. Just because you have water next to land does not mean you can actually drive off a road into the water. For that you need a boat ramp, and while there are a few (maybe 3-4) such ramps in San Francisco, you will find that using them is a lot less convenient than driving across a bridge and you will need to go far out of your way to do that.

It is about 9 times faster on land than on water, so unless the bridge was quite congested it would still likely be faster. If the bridge is so congested that it is faster than taking that car in the water, the roads after the bridge are probably also congested so all you gain is jumping ahead in the congestion.

The situations where the bridge is very slow but past the bridge is not are probably sufficiently rare that it is not worth the extra complexity of an amphibious car for most people.

It might be more interesting and attractive in places without bridges. Depending on the speed and frequency of a ferry service, it is possible that the car on water would be faster.

Ferries will usually travel faster (the Seattle car ferries are around 2.5 times as fast as the Amphicar, and the fast passenger ferries are about 5 times as fast), but the Amphicar could still win if you have to wait a long time between ferries.

For example, the car would take about 2 hours to go from Seattle to Bremerton via the water. The state ferry on the same route would take about an hour, but the ferries are almost 2.5 hours apart so it would take you from 1 hour to 3.5 hours by ferry depending on how your trip aligns with the ferry schedule. (The car could do it in 90 minutes if you went by land instead, but that route goes through Seattle and Tacoma, so you could hit a lot of traffic which could slow you down considerably).

> What are people expecting?

A safe experience. There is always risk involved but floating things are a solved problem.

> They're 75yo vehicles who's capacity and seaworthiness were defined relative to very different cultural norms regarding safety and a national emergency that necessitated acceptance of some additional risk.

Duck boats are antiquated military vehicles which are modified by their owners via cutting them in half and extending them. One owner did the work himself with little to no experience in that area with zero engineering oversight. Basically the guy winged it and people died.