Beach · Barnstable County · MA
Is Seconsett Island Causeway safe to swim?
Recent heavy rain may have spiked bacteria since the last clear sample.
Updated July 19, 2026 · Massachusetts beach program (EPA BEACON)
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What's in the water at Seconsett Island Causeway right now
As of July 19, 2026, Seconsett Island Causeway in Barnstable County, Massachusetts carries a swim caution. Blue-green algae are not currently monitored at this water. No fecal-bacteria advisory is posted (state beach program). Rainfall over the past week totaled 2.4 in, which can wash bacteria and nutrients into the water.
Blue-green algae at Seconsett Island Causeway
Seconsett Island Causeway is a lake in Barnstable County, Massachusetts. Blue-green algae are not currently monitored at this water.
Blue-green algae (cyanobacteria) blooms are most common from midsummer into early fall, when the water is warm, calm, and rich in nutrients from runoff. They can produce toxins that make people sick and can be rapidly fatal to dogs, so skip water that looks green, scummy, or like spilled paint, and keep children and pets out of it.
Frequently asked: swimming in Seconsett Island Causeway
- Is it safe to swim in Seconsett Island Causeway right now?
- Seconsett Island Causeway carries a swim caution today. Blue-green algae are not currently monitored at this water. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.
- Does Seconsett Island Causeway have blue-green algae (cyanobacteria)?
- Blue-green algae are not currently monitored at Seconsett Island Causeway. Watch for green, blue-green, or paint-like scum and avoid the water if you see it.
- Can dogs swim in Seconsett Island Causeway?
- No bloom is detected at Seconsett Island Causeway today, but dogs are much more vulnerable to blue-green algae than people, and blooms can form within hours. Always keep dogs away from water that looks green, scummy, or discolored, and rinse them off after swimming.
- How many Massachusetts lakes and beaches have swim advisories today?
- Today, 5 Massachusetts waters are under a swim advisory and 229 more warrant caution, out of 608 monitored waters SwimZone tracks in the state.
- How is Seconsett Island Causeway's water quality measured?
- SwimZone builds this read from EPA CyAN satellite imagery for blue-green algae, official beach and fecal-bacteria advisories where a program monitors Seconsett Island Causeway, and a recent-rainfall overlay, all refreshed daily. It was last updated July 19, 2026.