Create default creatures which actually look like fishes

[larister]

[orangespaceman]

I made a quick start on this, it would be good to extend them so that they use a full range of available functionality.

I think it's also fine to point people at the creatures in the jungle repo to further demonstrate possibilities.

I'm happy to do this one, feel free to assign it to me.

[larister]

Aces thanks @thegingerbloke; yeah I'd like to extend the docs to make it more clear what's possible.

[orangespaceman]

I think these are OK now, let me know if you think there's anything obvious we're missing