About a hundred dynamic pile tests using the Pile Driving Analyzer were performed for an LNG marine facility in Indonesia. This paper presents the application of the CAPWAP^® impedance model to interpret unusual dynamic test records of five tubular piles. Three were top closed-ended piles constructed by sand-filling the upper pile segment above the soil plug after initial driving and splicing a closed-bottom extension segment to the pile top. Two of the extended piles were further driven to deeper penetrations, and a dynamic test was performed at the final installation. However, one of these piles was tested directly after splicing without further redriving; this provided crucial information for verifying the impedance model. Two piles were bottom-closed at 6 m above the pile toe. The force (F) and velocity (V) traces of all but one indicated unusual separation/deviation. This deviation was usually attributed to the shaft friction but was found inapplicable in this case. Instead, the pile close-ended condition trapped the porewater in the sand fill and created a virtually incompressible pile-soil-water system. This high incompressibility, in turn, caused a significant increase in its impedance, which proved to be the cause of the separation/deviation. Applying the CAPWAP model, the pattern of the increase in impedance at the best match proved to be consistent with the boundary conditions. The top closed-ended pile showed the highest increase in impedance over the upper half and then tapered off toward the pile toe, i.e., where the excess porewater pressure could dissipate. Similarly, the highest increase occurred at the most undrained condition at 6 m from the pile toe for the two bottom-closed piles. Furthermore, the test record of the one pile that was not driven deeper prior to testing showed no unusual separation/deviation. The success of the increase-in-impedance model eliminated the need to incorrectly add more shaft friction to the bearing capacity to achieve CAPWAP best match.