The health benefits of fish and fish lipid consumption have been proven and, amongst the active molecules, n–3 long-chain fatty acids (n–3 LC-PUFA, notably EPA and DHA) have been put forward. Currently, seafood is the primary dietary source of EPA and DHA, but specific dietary supplements are also being developed, including fish oil capsules and the design of specific molecular carriers. The aims of this chapter are to (1) summarize the lipid composition and specificity in fish and fish oils, (2) define their molecular and supramolecular carrier forms in different food products and supplements, (3) discuss their fate during digestion which partly determines their bioaccessibility, and (4) review their health or metabolic impact as related to the supplied form. Finally, further thoughts are provided to better address this topic from the formulation, food or supplement processing viewpoint. Reviews are provided of specific metabolic studies evaluating fish oil bioavailability.