Everything appears to be correct except that your conjugation for “nadar” doesn’t match your pronoun “nosotros.” “Nadan”, as you have it, fits with 3rd person plural (Uds, ellos, ellas), so replace that with “nadamos” and you should be good!
<h3>Question - ¿Tus hermanos y tú nadan en el mar?</h3>
Answer: Nosotros no nadamos en el mar.
We do not swim in the sea.
Explanation: the subject in this sentence is "mis hermanos y yo", which is the first person in the plural, so the verb must be conjugated in this form. Nosotros no nadamos.
