There are two correct answers to this question. For the first question, the correct answer is swimming. To the second question, the correct answer is a gerund. In this sentence, the verb is swimming. This word is a gerund. To be able to identify what type of verb swimming is, one must understand the meanings of the types of verbs.
A gerund is a verb that ends with "ing." A participle is a word that is created from a verb, like going and gone. An infinitive is a verb with no connection to the subject, like "we came to see." Knowing these terms, we can identify that swimming is a gerund.