Cashla Bay is located on the west coast of Ireland, south of Galway, and is considered one of the most sheltered anchorages along this stretch of coastline. Its protected character makes it accessible even under storm conditions, which speaks to its generally calm water environment relative to the exposed Atlantic coast nearby.

The bay sits within a broader coastal landscape characterized by rocks, islands, and intricate passages. Neighboring water bodies include Greatman's Bay, Kilkieran Bay, and Bertraghboy Bay, all of which offer complex coastal paddling through a coast studded with islands and channels. The area also serves as a practical base for those wishing to explore the Aran Islands — Inis Mór, Inis Meáin, and Inis Óirr — which lie out in Galway Bay.

The bay has historical significance as the site of a pier built by naval architect Alexandre Nimmo in 1823 at Costelo, now part of the expanded Rossaveel Harbour complex. A Martello Tower also stands in the area, reflecting the bay's long history of maritime use.

The broader coastline is described as intricate and rock-studded, suggesting paddlers should exercise appropriate caution regarding submerged and exposed rocks throughout the area. The presence of Rossaveel Harbour within the bay means there is likely commercial and ferry traffic in the vicinity, which paddlers should factor into route planning, particularly given ferry services to the Aran Islands operate from Rossaveel.