Don't Draw "Extreme Sports" Without Reference
Exhibit A (Surfing):
I presume these two are supposed to be "surf-boarding"? Or one of them is, at any rate. What is that chick in the back doing? Can she fly? Should I assume that? Ok, let's give them the benefit of the doubt on that one and proceed to the "surf-boarding" in question. Has anyone out there ever seen real surfing? Show your hands. Either a surf video or actual surfing? Yes? Then this should look very weird to you.
You know what, this should look weird to you even if you only have a vague idea of what surfing looks like. What is the "surfer" doing? Bursting out of the water from beneath the wave? Look at the angle that nose is coming out at! And while we're on the nose, that's a mighty wide board. Perhaps a fish? But I doubt the artist knows what a fish is. "Look, it's a surfboard! It has a tapered nose!"
Let us also examine chicky-pant's foot placement. Her front foot is...well, probably not even touching the board given the angle of the board relative to the angle of her calf. But even if her foot were contorted enough to be flat on the board, it would be somewhere around the end of the nose. Something even Wilbur Kookmeyer would make fun of. And her back foot is presumably plunged three to five feet underwater with the rest of the tail. Then we have the rest of her body, which seems poised for something, if not the activity at hand.
Wait...is she wearing bracelets? Big loose bangles? While surfing? It also appears that she is wearing a thong bikini. The sort of thong that is going spelunking. Very tasteful. Finally, there's the water, that appears to be made up of the same material as the sentient goo from The Abyss.
The image was taken from a preview for some comic called "Koni Waves." It's about [no idea] fighting [who cares] in HAWAII. So this just compounds the offense. You're writing and illustrating a book that takes place in Hawaii, the birthplace of surfing, and you're not going to research how surfing actually looks? Please, Mr. Artist, do a 2-second Google image search and learn something. There's a reason the great artists always say "use reference!" when asked for advice in interviews.
(I've got similar things to say about skateboarding, but I don't have any examples in front of me at the moment. When I find some offenders, they'll go up.)