The Underwater Observatory Park is actually an amalgam of sites directly on the Red Sea and you can easily spend a full day there. The most noticeable is a large observatory that goes below water and allows you to observe life on a created coral reef. You can also climb up the tower of the observatory and see Jordan and Egypt and eat lunch there. The park also has a shark tank and several aquarium exhibits, as well as revolving exhibitions. These are mostly standard and in-line with what you would see at any good aquarium.
Additionally, the park offers a chance to ride in a *real* submarine (the Yellow Submarine) out to a reef wall. DO IT! It's a bit expensive, but worth every dollar (especially if they are running specials). The Oceanarium: a 'motion' ride was very cheesy, poorly dubbed into English, and really not worth the effort unless the kids are into those kind of rides.