Try to float onto your back

From Create Your Own Story

You float onto your back and that makes it easier. You drift over to the island. When you make it to the shore, you bang your head on the rock and you get a minor concussion. Before it can get any worse, you grab onto the island, but just when you are about to pull yourself up, some kelp attaches to you and gets caught. It is short, so it's pulling you into the water.

Get pissed off at the kelp

Try to sever it off

Ask the Dursleys for some help

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