Bubbles:
Curiously, when Aristotle described an elephant he stated that they could breathe underwater with their long nose. He described this as being exactly what divers do when they breathe through a tube to the surface.
On the parts of animals
Just then as divers are sometimes provided with instruments for respiration, through which they can draw air from above the water, and thus may remain for a long time under the sea, so also have elephants been furnished by nature with their lengthened nostril; and, whenever they have to traverse the water, they lift this up above the surface and breathe through it.
Not exactly SCUBA, but it is a natural method - - and the description is 2,400 years old. :sheik: