Loch Sunart is a sea loch, fed by burns and streams from the surrounding hills, and with salt water from the Atlantic Ocean. The convoluted coastline of the loch creates sheltered habitats while at its mouth Atlantic currents and strong tides make for turbulent transition from loch to sea.
Loch Sunart lies where warm southerly seas meet colder northern waters, there is an exciting mix here of marine life species. For example, from the north comes the sponge and the small spiky snow-white anemone, while from the south comes red sea finger. Along the tidal shore different species live in clearly defined zones, with colourful lichens on the upper shore, sea weeds in the middle, and barnacles and kelp on the lower shore. Most seaweeds attach themselves to rocks, but in sheltered parts of Loch Sunart lives rare free-living form of egg wrack, a popular hunting ground for young otters. On calm summers days at low tide you can see masses of brittlestars along the shore between Salen and Glenborrodale.
At its deepest point the loch is 124 metres deep, and the bed of the loch varies dramatically, from muddy basins to rocky reefs. In the deep basins lives the tall sea pen, which stands over two metres high! The steep underwater rock slopes are home to organisms which thrive in the strong currents.
Loch Sunart is home to flame shells, which combine to form a hard reef to which other reef animals and plants attach. The flame shells here may occur at densities of up to 400 per square metre!