To be honest, these two are one of my top 3 otps as of now. Despite them having no history together, and just have practically met, their personalities and opinions actually compliments eachother.
Diego does some really stupid stuff sometimes (like above), and even though Chel is keeping her pokerface there, she's amused and enjoys the types of shenanigans Diego puts on. As you've seen in one of the comics, she pranks Diego herself, and are also sometimes an asshole like Diego is. I could go on and on, but then it might get spoilery, so I'll stop here.
I could put them in so much situations and it just works, it's so awesome god I love this pairing so much.
This may well be the greatest seducing technique ever conceived. Now, if only Diego kept his usual smug face, Chel would have fallen head over heels for him! But sadly for him, he makes a very derp-looking expression... Which is great for us because it's hilarious! XD