system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why eating salty food makes you retain liquids, but drinking ocean water would kill you from dehydration?
gpt
When you consume a lot of salt, your kidneys need extra water to process it.  It gets that water by making you feel thirsty and drink more water, and holding that water in reserve for your kidneys.

Your body actually handles both saltwater and salty food in the same way.  You are only in danger of dehydration if you don't have access to regular water after.  If you drank seawater followed by regular water, you'd retain water and be fine, if you ate a bunch of salty food without drinking after, you'd risk dehydration.