The exhibit is horrendous for the tapirs due to lack of space and lack of natural substrate on land, and I've always been under the impression that they could not access the higher ground. I don't think that it would be too difficult to place small-clawed otters in the exhibit, but the zoo has held tapirs here for almost 20 years.
I've personally seen several tapirs at a few different zoos and, in the case of one zoo, seen them many, many times and to this day I've not once seen a tapir in the water. In fact, I've only ever seen them either resting like this or walking around the land area.
Whenever I go to the Detroit zoo, the tapirs are always floating in the water like hippos. Out of 15 or so times, only once or twice did I see them resting in the sun. Those were Lowland Tapirs, though......