I think Smith probably just floated off the ship, in such a manner that Harold Bride stated.
Captain William Turner did the same thing on the Lusitania (although he survived).

Really, would one want to really be inside a sinking ship's wheelhouse? I think I'd rather die of hypothermia from cold water than actually taking water in my lungs and dying painfully from drowning.

On the subject of his body never being found, that is one point I always thought was so horrifying about the sinking. Where did those bodies go?

Aparently, Officer Lowe stated that there were so many bodies at the scene of the sinking when he returned that he could not row through.

But the next morning, Rostron only saw one body floating. Did the current take them away that quickly?

In the end, the Mackey Bennatt and (the other ships......???) only found about 300 bodies out of 1500. It makes you wonder how many people were trapped in the ship, and how many just did not get recovered and eventually desentigrated into the water.