Swimmable.fyi
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About Swimmable.fyi

A plain-language read on swim conditions, spot by spot. Here's how we get there, and where the numbers come from.

Reading the water

A shoreline isn't a pool. The water itself moves, on a schedule: twice a day the tide pushes water in, and twice a day it drains back out.

flood: water flows inebb: water flows outslack: calm pause
  • Flood: the tide coming in. Water flows in from the open ocean.
  • Ebb: the tide going out. Water flows back to sea; in an enclosed bay or inlet this is often the stronger flow, and the one that can carry you away from shore.
  • Slack: the pause while the tide reverses, roughly every six hours. The water is nearly still, which makes it the easiest and safest window to swim.

Wind direction is where the wind blows from. A southwest wind moves air from the southwest toward the northeast. Wind blowing in off the water stirs up chop that makes breathing and sighting harder; wind blowing out from shore can look deceptively calm near the beach while pushing floats and swimmers outward.

How we calculate this

Use it from your AI agent

Add Swimmable.fyi to Claude Code. No install, it runs over the web.

claude mcp add --transport http swimmable https://swimmable.fyi/mcp

Bacteria comes from each region's own public program, weekly: San Francisco's Beach Water Quality feed, California's statewide beach water quality program for San Diego. Tides and currents from NOAA CO-OPS.

Curious what a spot's own data looks like? Browse the registry.