What does squid, octopus, mussels, and clams taste like?

You are generally right. Clams and Squid might taste similar if fried.

squid is chewy and doesn't have a lot of flavor from my experiences eating it both cooked and raw as sushi - i would say it can be likened to tasting like a mild flavored white fish octopus is more chewy then squid and also does not have a lot of flavor unless you eat one whole then it tastes a bit oceany and the ink sac has a distinctive flavor i found to be bitter - i like octopus over squid for flavor and texture but a lot of people don't like how chewy it can be mussels to me taste oceany like how the ocean smells and clam-like but with more of a distinctive flavor that tells you it's a mussel and not a clam - green mussels are awesome clams taste like well, clams... mildy briny, sometimes gritty, tender, ... great with garlic butter dip ... crab tastes sweet and similiar to lobster - i like crab better then lobster try some crawfish aka. craw dads/mud bugs sometimes too!

They are all delicious.