A seal.
Its a seal.
swims (SWIMS)
barks
SWIMS
Nocturnal mammal: bat
SWIMS
koala
Otter
bat
As long as it is in all capitals, the word "SWIMS" can be read upside down.
SWIMS
seal
The answer is cutch.It's five letters, ending in H. Cutch is an extract of tannin which comes from several barks of mangroves in the Pacific areas of the globe.