Despite the fact that marine litter is recognized as one of the main problems in the world, its quantity and level of influence continues to grow. It reaches the sea through the conscious and unconscious actions of man and brings numerous negative impacts on the environment, economy and society. Although numerous qualitative-quantitative studies have been conducted so far on the accumulation of the marine litter on the seabed, on beaches or in the open sea, information for the areas such as nautical marinas and harbours is rare. This paper presents the results of the analysis of the qualitative-quantitative composition of the marine litter collected on the seabed of the ACI marina Split and the port Spinut in Split. 201 pieces of the marine litter with a total weight of 87.51 kg were found at the bottom of the ACI marina Split, while 45 pieces with a total weight of 31.61 kg were found at the bottom of the harbour Spinut. The density of marine litter at the bottom of ACI marina Split is 2.5 pieces/m², while at the port of the Spinut is 0.6 pieces/m². In addition to the above, marine litter analyses were made for each main category of the litter: plastic, glass-ceramic, fabric, metal, rubber, construction material, wood, paper and others.