It seems some species of Ceramium (Red alga)

1762: a nemertean worm

1763, 1765, 1767: Ceramium

1823: a polychaete, possibly of the family Phyllodocidae

Thank you Godfried and Arvind 

certainly not a seaweed

Number 1 and 5 are warms

#2-4 are red species of the genus Ceramium, Pictures don't give enough data to identify the species.

thank you Razy Hoffman

Yes it is Ceramium confirmed because I have identified this last month but for species check proper details. Try to get fresh sample for identification, you will get good images.

I agree with Godfried.  The first and last photos are of a nemertean and the last has parapodia somewhat like the Phyllodocidae.