[2][3] Chorda filum have typically long, unbranched and hollow rope-like brown fronds about 5 mm (0.20 in) in diameter but can reach to lengths of 8 m (26 ft).

[4] C. filum is found in sheltered marine and estuarine bodies of water at depths of up to 5 m (16 ft).

C. filum grow at an average of 17 cm (6.7 in) per month, with the spiral-shaped, often gas-inflated, termini of fronds being dead, but receiving replacement by growth from a sub-terminal meristem.

However H. tomentosus is less common and is covered with long brown paraphyses or sterile hairs.

[7] It may be common or abundant near low water and in the sublittoral to 25 m (82 ft) areas in mud and sand.