This data set is comprised of one table with sampling information and NCBI BioProject accession numbers for sequence information of this amplicon-based study targeting Labyrinthula, Phytophthora, and Halophytophthora of known pathogenic and non-pathogenic [to eelgrass (Zostera marina)] strains from eDNA samples. eDNA samples included water, sediment, and eelgrass from Notsuke Wan (Cove) Japan, Safety Sound, Izembek Lagoon, Port Moller, Chignik Lagoon, and Frederick Sound, Alaska and cloacal swabs from waterfowl hunted near Cold Bay Alaska. Replicate samples and multiple sampling dates of the same location were included. Highly conserved primers which could differentiate species of interest were developed for four portions of mtDNA genes (5.8S, 18S, ITS, and COI). The reference list and conserved primer sets to identify species present were developed using publicly available data https://www.ncbi.nlm.nih.gov/genbank/