Seria Beach runs along the coast road that passes the Billionth Barrel Monument, and it is worth a slow walk rather than a dedicated visit. The beach itself is simple — no beach bars, no loungers, no obvious amenity — but the view makes it worth stopping for. Offshore oil platforms dot the horizon, and the coastal strip is punctuated by pump jacks that have been here for decades. The contrast between the calm sea and the workaday oil infrastructure gives the place an atmosphere you will not find on Brunei's more polished tourist coastlines.
Sunset is the best time to come. The light hits the pump jacks and the distant platforms in a way that is genuinely photogenic, and the coast road is quiet enough in the evenings to walk comfortably. If you are combining it with a visit to the Billionth Barrel Monument, the two are within easy walking distance of each other.