Which marine pairings typically exhibits mutualism? barnacles/mussels clownfish/anemone shark/sea lion tapeworm/manatee

I believe the answer is: clownfish/anemone

Clownfish is very territorial in nature. So, when they hide within the anemone, the clownfish would prevent smaller fishes from eating the anemone. In return, the anemone would prevent the bigger fish from reaching the clownfish when they hide in it.