water part, ideas for the changing as details for how it happens.
*the horns cracks into parts, letting the fleshy segment grow into sensing prob to detect changes from behind and temperature of the water or ripplings on the water-surface when resting.
*outer fur drops while the inner and closest absorbs and grows into a thicker skin over the whole body
*longer segments in the bone structure of the tail, cartilage that grows from the sides to form the fin structure
*does not breath in water, have to come up to breath air and sunbath to regain warmth for deeper dives