One of the sightseeing tours of Singapore is called the Ducktour, and uses an amphibious vehicle used by the US military in the Vietnam war. They were bought by an enterprising travel company and used for these Ducktours where people are taken on a 1 hour trip, starting with a building in the Suntec City. These go through the city and then head for the Singapore river where they go for a short trip around some of the prominent landmarks of the city. It is an enjoyable tour and seemed fairly safe.
In this photo, taken from near the middle of the vehicle, as it starts on the tour, one can see visitors sitting along with the cockpit like driver's seat of the vehicle. Attached to the top section of the vehicle are 2 flotation devices along with some instructions.