I think where you go with this sentence is dependent upon a number of things:
-what is the purpose and tone of your piece? Is it ominous? Is it sad? Is it injected with humor (dark though that might be)? You want to find a similie that reflects the tone of the piece and brings the reader closer to whatever your purpose is
-I love the idea of just listing as many things as you can think of and then finding what strikes you. I would even say combine that suggestion with the one above about keep writing and then come back. Write a list right now, then leave it alone and keep writing. Then come back to your sentence and your list and see what comes up out of your brain
-Think about what you think the smell actually smells like and then go one of two ways: use a similie that reflects that smell or use a similie that is completely the opposite. I love the juxtaposition of different ideas in creative writing.
-I love #3's idea about the dead crab smell. It cracks me up!