As said GBB is the govt project, it must provide the relevant
transport required to supplment the crowd.
The whole marina bay side is a reclaim land, some part are soft
soil, eg GBB and many other places, reclaim land needs few years
for soil to solidify and claim again, so you can see there is no
tall or big structure at marina bay, and that is why LKY said, make
a garden out of the city wall jungle and at the same time, make
money.
Marina Barrage is a civil structure for the purpose of
commerical, that is to control and water flow and supply, it is
like any other water control station, just that it was built in a
nice location with good view, govt just add on some attraction like
most reservoirs in Singapore. Its free.
Marina ferry pier is a private entity, it consist of many pte
water taxis services, from Penguin to York..and so on. It provide
boat and ferry to kusu, western and eastern anchorge, and also
a sign off and in place for ship crews, including me if I sail
on contract. They also provide OPL (out of port limit) services,
this one you go into international water to service ship. Per trip
from marina pier to eastern anchorage (those ships you see at ECP),
cost about $120.