Trident Archaeology was commissioned by WSP to carry out an IVO underwater evaluation (protocol 4103) of GR-2, an anomaly that had been highlighted as of possible archaeological interest. The anomaly is located in the Grevenligenmeer, approximately 100 m southeast off the Preekhillpolder, near Ouddorp. The investigation resulted in the identification of the timber at the anomaly location as part of the stem assembly of a wooden ship. The timber was probablysourced in England and the parent tree was felled at the end of the 16th century.

Trident Archaeology was commissioned by WSP to carry out an IVO underwater evaluation (protocol 4103) of OM-11, an anomaly that had been highlighted as of possible archaeological interest located in the Oude Maas, along Hongerlandsedijk, Spijkenisse.The site is a clay mound measuring roughly 4 by 2 meters with irregular edges that rises approximately 0.3 meters above the river-bed. The materials found at the location included natural wood (tree stumps and raw wood), a small number of processed timbers (two posts and two boards), modern waste, a limited number of pottery fragments that date from the late medieval period, five fragments of clay pipe stems, five fragments of animal bones, and fragments of bricks. The variety and composition of the assemblage together with the fact that the finds were recovered from a mobile superficial sandy layer seems to indicate that this is a natural feature that acted as a trap for various debris carried downstream by the river rather than a feature of archaeological interest.