I have mostly seen curiosity and fear, but the fear isn't so much a real tangiable fear that we as humans may feel if we encounter a wild animal. Fish and most marine life have a personal space bubble, similar to humans and if you enter their space they will move or swim away. My encounters with sea lions is very unique in that they can see their own refection in a diving mask and then will react accordingly, maybe blowing bubbles or moving their heads back and forth. They are not self aware so they react similarly to other animals like bears when they encounter a mirror in a forest that may be there for scientific purposes.