Rubbery clump of sand?

[Rirule]

This morning i found a clump of sand, tried to touch it with some tweezer and it seemed rubbery, elastic.
I have a conch that regularly clean the sand bed and i don't know what it can be?

Edit: added another more zoomed in pic

 

[Timfish]

Mucus from various worms or snails can potentially cause that. Some sponges can also but I'd put my money on a snail in this case.

 

[Rirule]

I'd put my money on a snail in this case.

Probably the strombus then, he is cleaning the sand like a maniac! Thanks