Along Singapore River, near Jiak Kim bridge.
Question 1: Why do the otters go on land?
I have seen the otters:
a) sleeping under Jiak Kim bridge;
b) rolling on sand and grass patches (at Marina East, see http://cethosia.blogspot.com/2015/11/marina-east-2015-november-28.html and Gardens by the Bay, as well);
c) resting on grass patch (at Marina East).
Question 2: How do they get in and out of the water?
a) Staircases around Jiak Kim bridge;
b) sloped embankment at Marina bay.
Other observations:
I have seen the otters swimming further upstream near Zion Riverside food centre but there is no staircase or sloped embankment upstream from Jiak Kim bridge.
Downstream from Robertson bridge, there is no sand or grass patches.
Conclusion: The conditions at Jiak Kim bridge are just right for the otters!