Don't worry, anyone who thinks the crab is too short to block the goal: if they're a member of e.g. families Portunidae/Ovalipidae (distinctly possible as at most three pairs of walking legs are visible), they can swim using rear paddles.

(For those who say the chelipeds aren't the right shape: shhhh.)

It’s also under water so it can swim up

I got Liz climo vibes ☺️☺️☺️

It can only run sideways because they're a crab, not because their legs are stiff.
Yes, the legs are "stiff" in one direction because of their anatomy but it's like a human saying "I can't hang by my tail because I lost it".

This is basically the plot of Escape To Victory.

I really don't want to be a downer, but the title kind of make this a flawed message. The shark can miraculously hold a football, but the place of the crab is only as a goalie? I believe there's always a way, but we are not naturally limited to a small set of positions.

I'm more interested in what position the clownfish has