It’s important to remember that wooper don’t have arms, which sounds like stating the obvious, but it’s very easy to forget how, specifically, all wooper interact with objects given to them.
That is to say, don’t give your baby wooper anything that can fit in their mouths. They will very likely try to eat them. Yet at the same time, it’s also fine to give them things they can grip with their jaws—just … nothing that they can swallow.
On that note, two wooper may enjoy a length of rope to tug between themselves. There are thick, braided cords sold as arcanine toys at practically every pokémart; these will do just fine for wooper, as they tend to be just large enough for them to grip.
Alternatively, provide them with larger floating toys, such as inflated beach balls, inner tubes, or pool noodles. Wooper will often push these about their ponds or to each other, and even just one pool noodle will provide endless hours of fun for them. Just be sure that your wooper don’t attempt to bite off chunks as they get older. Most will understand that their toys are not for eating as they age, but keep an eye out if one or both of your wooper turn out to have voracious appetites.
Finally, in their habitats, it’s worth constructing small hiding spots or play equipment such as artificial caves, and be sure to install a few (edible) plants at the bottom of their pools. Sometimes, wooper prefer to entertain themselves by swimming about their ponds, and the more interesting you make their habitat itself, the more interesting it will be for your wooper.
The Pokédex According to Bill 