You can put some toys in the exhibit, like balls, hoops to swim, buoys... Place the food in different places of the exhibit: in buoys, pipes, some places of the exhibit, high places... Try to make it not very easy, or the enrichment will not help; or very difficult, or the animal can get stressed. It is also good not stay in the same always: it is good to present the animal new things that it has never seen before (toys, food, challenges, friends...) Train the animal to do tricks is also an option, but I'm not a fan of this: what you teach for the animal making it rotate to have food? If I'm wrong or if you want to add some information, do it, please!
I trust that the keepers are aware of this group The Shape of Enrichment https://www.facebook.com/shapeofenrichment/?fref=ts
Indeed. One of my co-workers used to work at OKC recently, and they are quite on top of all the various enrichment groups.