How do I learn to swim 250m on my own?

So I'm trying to learn to swim 250m with no breaks for school, I don't feel comfortable swimming with the rest of the class and made a deal with my teacher that id tech myself and come with a certificate by the end of March. Now, I'm not completely hopeless at swimming, i can float and swim. My problem is that i get super tired in the arms after 10-15m and have to rest. My cardio is good normally, i can take 20-30min runs with no problem. People tend to say its about the form but i dont understand how. To be able to get the certificate i have to swim 250meters with no breaks. How do i teach myself to swim such a distance?


I'm a swimmer and I'm not quite sure what to tell you. Keep your head looking at the bottom of the pool, make sure you kick your legs so you're not relying on only your arms. Watch YouTube videos.


You need to start at a distance you can do and build up from there. Had five more meters a week. Perhaps trying some arm weights to build up your arm muscles would help.