Could this be a large, light-colored marine animal, which could be a shark or another large marine mammal, such as a manatee or possibly a dolphin, or perhaps something totally different altogether?
Participating in Six Word Saturday
Now, Let your imagination run wild
Ritva Sillanmäki Photography 
Tantalising.
This is such a fun and intriguing piece—you’ve captured a real sense of curiosity in just a few lines. The open-ended questioning pulls the reader right in, making us pause and imagine what it could be, almost like we’re there with you, trying to make sense of the sight.