A: Beth, sometimes I have a gift for figuring out the obvious. In your case I believe that the "fishy" smell in your bathroom may have something to do with the fact you live on the ocean. (I say this in fun.)

Now that we solved that mystery let's look at the problem that may be bringing odors into your home. Thanks for mentioning that you find sand in your lower level shower stall. This clue suggests that your septic system may flood from time to time, and some waste water may actually flow back into the lower level shower stall, bringing all the nasty stuff with it.

Basically, when the water recedes, it's low tide in your shower stall! You need to have a licensed septic company inspect, check and pump out your system, and this may stop the recent "wave" of odor problems you've been experiencing.