When I bought my first compass, I was shocked to see how much they charge for a few pieces of plastic and magnetic steel, so I bought the cheapest compass I could find, a Cetacea. A year later, I take it out of my dive bag one day, only to realize that one of the magnetic bars had detached from the rotating disc and rendered the compass useless. Trashed it and bought a used SK-7 online, which I am using now, bungeed on my wrist. What have I learned from this?
1) All compasses are not created equal
2) The SK7 is amazingly accurate and needs no time to adjust, unlike all other compasses I've seen.
3) It is important to treat your compass like any other expensive and fragile gauge. I now keep mine wrapped in a cloth, stowed away in a sturdy box. No more tossing into a scuba bag.
4) Stay away from cheap compasses, especially Cetacea