Dive with
Best places to dive with Troll Hair Algae
Filamentous freshwater algae (unidentified; locally 'trollahár')
The bright green filamentous algae that grows along Silfra's lava rock and is the most visible living thing in the fissure. Icelandic operators call it trollahár — troll hair. It is the reason the Lagoon reads green rather than grey, and it is the closest Silfra comes to a biology draw.
Destinations ranked by how reliably troll hair algae is seen. The bars show the likelihood by month — never a guarantee. See the full species page for more.
Silfra, Iceland
| Month | Likelihood |
|---|---|
| January | commonly seen |
| February | commonly seen |
| March | commonly seen |
| April | commonly seen |
| May | commonly seen |
| June | commonly seen |
| July | commonly seen |
| August | commonly seen |
| September | commonly seen |
| October | commonly seen |
| November | commonly seen |
| December | commonly seen |
Present year-round throughout the fissure; no seasonal peak. Most obvious in the shallow Lagoon where light reaches.