The bootlace (Chorda filum) is very distinctive because, yes, it looks like bootlaces! The long thin strands. slimy to the touch, are unlike any other seaweed species. Seen washed up on the strand line on sandy beaches is fine but sadly most of us will never see bootlace at its best. For that you need to go snorkelling, something I have never done and will never do now.
Bootlace grows in clusters along the lower shore and down to about five metres and when afloat in water the strands, which can grow up to an amazing twenty five feet long, stretch out in masses along the flow of the tide. It is, apparently, quite a sight and bootlace has earned the name of mermaid's tresses although it is also known as dead men's ropes!
It grows well during the summer months and then in autumn it starts to break down and this is the best time to see it on the shore. By winter it has totally gone and will start the cycle again the following spring.