His ability to survive is some sort of anomaly and could definately be described as a miracle. It is amazing that he survived that long and it is certainly remarkable. THere are quite a few factors working against him and it is suprising that he was able to find a way to work against them.
The man that survived 60 hours at the bottom of the Atlantic Ocean was the result of a miracle. Surviving at the bottom of the ocean in an upside down boat is nearly impossible. Yes, there might be some air pockets, but eventually the air will run out. Furthermore, the pressure at the bottom of the ocean will eventually collapse the inside of a boat, forcing in water. In short, a man surviving 60 hours at the bottom of the ocean had to be a miracle.
It is true that the man who survived for 60 hours in a sunken tugboat in the bottom of the Atlantic prayed for a miracle, and believes his survival and rescue are signs of a miracle. However, there is no way to prove that a divine miracle actually occurred. The upended tugboat that he was staying under acted as a sort of diving bell for the man who was trapped, allowing a large air pocket to occur that kept him safe for the 60 hours before his rescue. Had the bubble been too small, he would not have been able to survive for as long. However, it is physics, not a miracle, that saved the man trapped in the Atlantic for 60 hours.
This entirely depends on the definition of a miracle that one takes. In the religious sense, this does not constitute a miracle. The law of large numbers better explains incidences of individuals surviving or not surviving things against the odds. This fact alone does not suggest the involvement of a higher being.