It's clear that Katie's having fun here, it's great that it's just a simple girl gets gunged and enjoys it video, there's no rigged quiz, nor directorial actions, no attempt at acting horrified, just a girl clearly enjoying the sensations as the gunge pours down. If anything, I'd say this scene shows the limitations of the tank design (really a universal issue and not just specific to this scene) as the scene goes on and a gungey Katie enjoys herself, it cried out for additional gunge drops to surprise and excite our rather happy victim! The mixed gunge drop is well delivered (and harder to achieve than anyone thinks!) The playfully naughty side of sploshing isn't that easy to deliver, but it is all to evident here that Katie is really enjoying her gunging!