The Crystal Palace Diving Institute - reservoir - Dexter house cellar - Cretaceous beach Anomaly was an Anomaly linking a bay in the Cretaceous to different locations in the present. The present side of the Anomaly moved locations along a temporal fault line, from the Crystal Palace Diving Institute to a reservoir twenty miles away then to an urban neighbourhood basement, while the Cretaceous side's location stayed fixed. The Anomaly was underwater, which meant that the Dexter home's basement was flooded when the Anomaly opened there, whereas in the reservoir, water was drawn out through the Anomaly into the Cretaceous.
The Anomaly first opened in a swimming pool at the Crystal Palace Diving Institute, and a young Mosasaur came through and devoured Anthony Barton before returning through the Anomaly and it soon closed.
The next day, the Anomaly reopened twenty miles away in a reservoir, and the same Mosasaur (and Anthony barton's regurgitated remains) came through the Anomaly into the reservoir. While searching the reservoir for the Anomaly with Nick Cutter and Stephen Hart, a Special Forces diver accidentally swam through, and apparently died of shock on the other side before he could return through. Later, after being wounded by Connor Temple, the Mosasaur returned through the Anomaly, which closed again moments later.
The Anomaly subsequently reopened later that day, in the basement of the Dexter house in an urban neighbourhood. Floodwaters poured through the Anomaly into the basement from the Cretaceous bay, and a Hesperornis also came through (though it presumably returned through after some time). After the Home Office and Special Forces tracked down and contained the Anomaly in the flooded cellar, Cutter swam through into the Cretaceous in search of Helen. There, after meeting Helen on the bay's shore, Cutter was pulled by Stephen Hart and Tom Ryan back through the Anomaly by his scuba gear's pipe (though not before the same Mosasaur from the swimming pool and the reservoir damaged his scuba tank).
Afterwards, a team of Special Forces divers went through the Anomaly into the Cretaceous to retrieve Helen, and brought her back through to the present by force.
- This is the first Anomaly to the Cretaceous, as well as the first underwater Anomaly, that was encountered.