Most people spend at least some time lying on the sandy beaches and swimming. Often, even at busy summer weekends, it is possible to find a beach all to yourself at a picnic site or with a walk away from tourist areas.
Wildlife watching is very easy. You will have to be blind not to see elk and deer, and with a little looking will also see other animals. There are many short trails with written guides to help you understand what to look for. There is a park nature centre and park office to help you plan such adventures. There are also guided naturalist walks for small fees.