Goose barnacle growth rates measured from specimens collected in Celtic Sea in April 2018 dataset https://portal.medin.org.uk/portal/start.php?tpc=009_CEFAS8c33112e-03ff-498d-bc73-551fac4453cc This data resulted from an opportunistic interception of biofouled marine litter floating off the coast of Cornwall. A colony of goose barnacles ( *Lepas anatifera*) and a neustonic isopod *Idotea metallica *were found attached to the drifting litter. Both these species are not native to the UK. The interception was used as a case study to model the path of the drifting litter to a probable origin in the Western Atlantic, using the biological traits of the attached animals. This data contains photographic images, location map, and text describing the specimens collected from the litter, along with photos of the litter object. The floating litter was intercepted at 50.145 N 6.019 W between Cornwall and the Isles of Scilly on the 11/04/18 by the RV *Cefas Endeavour*. Forty-five individuals of goose barnacles were retained along with one specimen of the Isopod. Descriptions of each species are given. Measurements of the length of three goose barnacle plates (Capitellum, Scutum, and Carina) are included. By comparing total plate length against different growth rates, we could derive probable growth durations for each of the goose barnacle specimens and this was used to paramaterize our model. 20221123 20221122