Is the arch on these as high as the arch on the Ohana?

Not sure about the Ohana, but I can say the arch is higher than most other brands that I have owned, one of the first things i noticed when i put them on. Hope this helps.

Does the footbed get slippery and/or squeaky when wet?

Yes very slippery and dangerous. I’ve had 10 pair of olukai flip flops but the last two pair are impossible to walk in if they get wet. I love these flip Flops but after I busted my head on a side walk in front of my kids because these slippery flip flops, I have to switch brands. They are safe for a couple months but then become very dangerous. I notified Olukai and they offered a refund if I bought them directly from them but I didn’t so until they find an anti slip footbed like reefs I’m not buying anymore.

Do they get dirty easily?

Funny you should ask, the 2nd day I had these, because I was going to be pressure washing and these are made to be in water, I wore these. As you can see the bottom sides are white. I was in an area where I was washing red clay/dirt off of a sidewalk and house, and to my surprise they didn’t get very dirty at all. And the little dirty that they did get rinsed right off, so I think they should hold up pretty good and clean easy. Hope this helps.