Which camera is best for quality, focus, and durability?

I use my parents' Nikon D5100, but I've noticed it's not very good with motion/focusing. Is this true or is there a special setting for something like this?

Here's what I really want in a camera:
-good quality sunset pictures
-can focus on sunset and object in front
-has good quality
-can take action shots (hair-flip, water drops, lightning)
-slow shutter
-self-timer
-easy connection to computer

Extra things I would like:
-durable; underwater
-not very expensive

Which camera includes the most of these features?

The D5100 should be good for anything just like any dSLR out there. It's not a special setting per se. It's knowing what to do with the camera on a given situation. If you don't get what you want, most of the time, it's your fault.

If you stick with the same brand, the d3x.

but unless you can give us a specific max price your willing to pay…

we can't really help you

and if your looking for underwater capabilities, the only underwater specific cameras out there are cheap p&s's but you can get waterproof casings for any dslr, but they are usually over $1000

the d5100 should be able to do all of that very well, except the underwater stuff

you clearly just don't know how to use it…