Five minutes of pure bizarre — a small driverless pod-train running through a tunnel under the Huangpu, walls and ceiling pulsing with fibre-optic light shows while an English-Chinese voiceover announces "magma!" and "meteor shower!" at random. It is the slowest way to cross the river and by far the most expensive.
The Bund Sightseeing Tunnel is a Shanghai classic and definitely worth doing once. The cheaper, more interesting alternative is the regular Huangpu River ferry from the Jinling Road dock — 2 RMB and an actual view.