The man in the mind 30's would be considered rather attractive by most. He is tall, has the trained body of a swimmer and a face with elegant, but at the same time masculine and slightly rugged features.
Though already from the distance it is clear the he is quite the odd beeing, alien enough to send a faint shiver down most peoples spines.

His skin has a dark blue hue, when it is exposed to a light source it might look like it has a faint silvereish green sheen to it.
He has very long wellkept hair, wich is almost of pitchblack color. A person with keen eyes will notice that a a changing number of dark tendrils are slowly but constantly moving and size changing within the mass of hair. The next thing wich makes his wicked heritage obvious is a set of three fins of different size, wich are growing out of his head and the lower back. Depending on his emotional state they tend to raise or sink back down again.
A closer look upon his face shows more of his uncommon nature. His cunning eyes shine faintly in an inner crimson light. An other thing wich might look a bit distrubing about them is that he possesses an additional pair of transparant eyelids, behind the regular ones, wich he can close sideways instead of from top to bottom.
With a grin he reveals a mouth full of broad, brilliant white and razor sharp shark teeth. You might almost be relieved that it is just a single row of them and not multiple, like on other creatures of the sea. Last but not least, whith further inspection a set of on each side of his neck comes into view.
Now putting one and one together, the assumption comes to the mind that he must be some sort of deep-sea dweller. Though obviously he is able to survive outsie of the water without much of a problem.

Though there is even more to him than the eyes might see upon a first meeting. The slightly alien, yet humanoid form is just a guise he uses when he maneuvers among others.
Two menacing, bright crimson glowing eyes staring from within a large mass of amorphous, rubbery, almost liquid, yet solid blackness. It is constantly shifting and moving, tendrils and tentacles are growing, slithering around and disappear again.
Whomever gets close enough to that formless darkness might notice that the air cools down by a few degrees and all sounds around him become muffled and slightly distorted, almost like you try to hear while having the head under water.
Also there is an a bit undefinable mix of different feelings wich can settle down in the minds of an unheeding target. Self-doubt, paranoia and fear are just meant to name a few of these.