Watch out for that gooey yellow and black thing. It's a banana slug. Living in Florida for twenty years, I forgot about these things. The average banana slug is about seven or eight inches long. When I was in middle school, I would arm myself with them and fling them into my sister's hair.
I see these things every time I run on the trail through the redwoods at Sequoia Park. The day after it rains, these things are all over the place.
Another cool thing to do to slugs if you're bored is to salt them. I won't tell you how it works out. I don't want to spoil the surprise.