Coastal Water Quality Monitoring: What Shark Awareness Day Says About the Sea

TL;DR: Coastal water quality monitoring puts continuous IoT sensors on the outfalls, storm overflows and surface-water drains that discharge near the sea, so a spill or a pollution spike is caught in minutes rather than at the next scheduled sample. In 2025, 32 of England’s 449 designated bathing waters were still rated Poor, and the Environment Agency only lab-tests for bacteria during the summer bathing season. That leaves long gaps where nothing is watching what reaches the coast. On Shark Awareness Day, when a third of the world’s shark and ray species are threatened, the operational point is simple: healthy oceans start onshore. Coastal water quality monitoring gives councils, coastal estates and facilities teams a live view of discharge and quality, using radar level sensing at outfalls, multi-parameter water-quality instruments and cloud alerts.

Last updated: 14 July 2026

Key takeaways

• Coastal water quality monitoring uses continuous sensors and cloud alerts to watch what reaches the sea between scheduled samples.
• In 2025, 32 of England’s 449 designated bathing waters were rated Poor, down from 37 in 2024, while 87% were rated Excellent or Good.
• The Environment Agency samples bathing waters for E. coli and intestinal enterococci during the summer season only, leaving the rest of the year unmeasured.
• Storm overflows, agricultural runoff and surface-water drains are the main routes pollution takes to the coast, and most discharge unseen.
• A third of shark and ray species are threatened with extinction, and pollution is one of the pressures the IUCN records on marine life.
• The AQUAIOT Radar and iSPA-T water-quality system feed one dashboard that alerts the moment a discharge starts or a quality reading drifts.

What is coastal water quality monitoring?

Coastal water quality monitoring is the use of continuous IoT sensors and cloud alerts to track the discharges and water conditions that affect the sea, every day rather than in occasional summer samples. It watches the outfalls, storm overflows and surface-water drains that feed the coast, measuring level, flow and quality signals and raising an alarm when a reading drifts toward a pollution event. For a coastal council or estates team, it converts an annual classification into a live operational picture.

England designates 449 bathing waters, and each one sits downstream of a catchment full of pipes, drains and overflows. The Environment Agency lists storm overflows, agricultural runoff, birds, dogs and local misconnections as the routine pressures on those waters. Coastal water quality monitoring is the layer that makes those pressures visible in near real time, so a spill or a spike is caught while there is still time to warn bathers, close an outlet or dispatch a crew. It is the same shift from spot checks to live data that underpins our wider work on water quality monitoring across UK sites.

Why were 32 English bathing waters rated Poor in 2025?

England’s bathing waters keep improving overall, but a stubborn tail remains polluted enough to fail. In 2025 the classifications recorded 87% of waters as Excellent or Good and a record 297 rated Excellent, yet 32 were still rated Poor, the lowest standard, against 37 the year before. A Poor rating means the water regularly carries enough bacteria to pose a health risk to swimmers.

In 2025, 32 English bathing waters were classified as Poor, down from 37 in 2024, out of 449 designated sites.

The Environment Agency attributes the failures to complex, long-standing pressures: storm overflow discharges, agricultural and urban runoff, wildlife and misconnected drains. What these share is that they are intermittent and mostly invisible. A site can pass one week and fail the next after a single downpour drives a storm overflow or washes contaminated runoff off the land. That is precisely the pattern that occasional sampling misses and that coastal water quality monitoring is designed to expose.

What pollution reaches the sea, and how fast?

Most coastal pollution arrives through the same drainage network that protects towns from flooding, which is why it moves fast and often goes unrecorded. When rain overwhelms a combined sewer, a storm overflow discharges diluted sewage to a river or the sea to stop it backing up into homes. Surface-water drains carry road, roof and farmland runoff straight to the coast with no treatment at all. Both routes react to rainfall in minutes, long before a scheduled sample or a beach inspection can catch them.

The scale is now measured.

Monitored storm overflows in England spilled 291,492 times in 2025, a 35% fall on the previous year, with total duration down 48%.

The direction of travel is good, but the raw count shows how routinely overflows still operate. Regulation is tightening in response: under the Water (Special Measures) Act 2025, emergency overflows must report discharges in near real time within an hour, extending a duty that already applies to storm overflows. Under Section 82 of the Environment Act 2021, continuous water quality monitoring must be rolled out upstream and downstream of every storm overflow and treatment works by 2035. The regulatory expectation is already continuous; coastal water quality monitoring is how an estate or council meets it on its own assets rather than waiting for the sector. Our guides to combined sewer overflow monitoring and storm overflow monitoring go deeper on the reporting duties.

What does coastal water quality monitoring actually measure?

Coastal water quality monitoring measures two things together: whether a discharge is happening, and what condition the water is in around it. The Environment Agency’s official bathing water assessment relies on laboratory tests for E. coli and intestinal enterococci taken through the summer season, and continuous sensors do not replace that regulated bacterial sampling. What they add is the missing context between samples, so an operator knows when a discharge started, how long it ran and whether quality shifted while the labs were closed.

On the discharge side, the AQUAIOT Radar uses 60 GHz non-contact radar to measure level to within plus or minus 2 mm inside an outfall, overflow chamber or surface-water drain. Because it never touches the water, it keeps reading through foam, debris and tidal wetting, and it timestamps the exact moment a chamber starts to spill. On the quality side, the iSPA-T Multi-Parameter Water Quality Online Monitoring System tracks turbidity, dissolved oxygen, pH and conductivity through Specsens full-spectrum UV-Vis sensing, so a sudden rise in turbidity or a drop in dissolved oxygen flags a pollution event as it develops. Both feed the AQUAIOT Cloud over secure cellular and LoRaWAN telemetry, with threshold and rate-of-rise alerts by SMS, email and voice. This is the continuous layer that our continuous water quality monitoring approach is built around.

How does coastal water quality monitoring protect bathing waters and marine health?

Coastal water quality monitoring protects bathing waters and marine life by shortening the time between a pollution event and a response, which is the window in which harm accumulates. Shark Awareness Day on 14 July is a useful prompt: the IUCN records that a third of shark and ray species are now threatened with extinction, and while overfishing is the dominant driver, habitat loss and pollution are among the pressures it tracks on coastal ecosystems. What is discharged from the land does not stay near the beach; it moves out into the habitats those species depend on.

Source control is where an estate or council can actually act. Catching an overflow or a runoff spike at the outfall means it can be warned, isolated or investigated before it spreads, rather than confirmed days later by a failed sample. That earlier response is also what the Storm Overflows Discharge Reduction Plan is pushing toward, requiring every storm overflow near a designated bathing water to be improved by 2035. Coastal water quality monitoring turns that obligation into daily operational data, and it links naturally to the pollution source-control work in our sewer monitoring service and our reporting on water pollution monitoring for UK rivers. Healthier bathing waters and healthier oceans start with knowing, in minutes, what is leaving the land.

Frequently asked questions

What is coastal water quality monitoring?

Coastal water quality monitoring is the continuous use of IoT sensors and cloud alerts to track discharges and water conditions that affect the sea. It watches outfalls, storm overflows and surface-water drains for level, flow and quality changes, and alerts operators the moment a pollution event begins, rather than waiting for a scheduled bathing water sample.

Does continuous monitoring replace Environment Agency bathing water testing?

No. The Environment Agency’s classification relies on laboratory tests for E. coli and intestinal enterococci taken during the summer bathing season, and that regulated sampling remains the legal standard. Continuous sensors add the context between those samples, detecting when a discharge occurs and how water quality shifts, so operators can respond before the next official test.

How many English bathing waters were rated Poor in 2025?

In 2025, 32 of England’s 449 designated bathing waters were rated Poor, the lowest classification, down from 37 in 2024. At the same time 87% were rated Excellent or Good and 297 were rated Excellent, the highest number since the current standards began in 2015.

Which AQUAIOT products support coastal water quality monitoring?

The AQUAIOT Radar measures level to within plus or minus 2 mm at outfalls and overflow chambers to timestamp discharges, and the iSPA-T Multi-Parameter Water Quality Online Monitoring System tracks turbidity, dissolved oxygen, pH and conductivity. Both report to the AQUAIOT Cloud with threshold alerts by SMS, email and voice over secure cellular and LoRaWAN telemetry.

Coastal water quality monitoring will not clean a catchment on its own, but it removes the biggest weakness in protecting the coast: not knowing a discharge has happened until the water has already carried it out to sea. For coastal councils, ports, marinas and public-sector estates, that live visibility is the difference between reacting to a failed sample and preventing the spill from mattering. To scope coastal water quality monitoring for your site, speak to the AQUAIOT water quality team.

By Gianbattista Porru, Digital and IoT lead at AQUAIOT.