Adhesives produced by marine organisms are fascinating in that they often possess an ability to adsorb rapidly and robustly to a range of substrates, in a range of environmental conditions and in the presence of significant surface contamination. On top of this, they undergo curing while in contact with water. Many of the properties that make marine bioadhesives so effective remain elusive to engineers designing synthetic adhesives. An increased understanding of marine bioadhesives would allow for the design of effective, biologically-inspired adhesives with applications in the engineering, maritime and health sectors. Conversely, better understanding of the adhesives produced by fouling organisms could help with the design of new fouling-resistant surfaces. One essential element for characterising a bioadhesive is to assess its adhesion strength to the substrate. In this thesis, I present a novel flow channel apparatus for testing the adhesion strength of marine organisms to help characterise their associated adhesives. The flow channel was used with Hormosira banksii and Durvillaea antarctica, two marine macroalgae endemic to New Zealand, and assessments of adhesion strength are made with substrates of varied chemistry and topography. H. banksii zygotes were found to exhibit a settlement-time dependent increase in adhesion strength across all of the biomedical substrates, which included poly(methyl methacrylate) (PMMA) and three hydrogels, two of which were gelatin-based approximations of human skin. H. banksii did not exhibit any substrate-dependent variation in adhesive strength, suggesting an adhesive that is able to interact with a range of substrate types. D. antarctica exhibited more rapid adhesion to glass, PMMA, PTFE and stainless steel than did H. banksii, forming a particularly strong bond with stainless steel. On substrates with simple, defined topographies, H. banksii zygotes were found to adhere most effectively to a surface with a feature size slightly larger than the size of the zygote. A feature size smaller than the zygote resulted in a minor disruption of adhesion strength that diminished with settlement time.