I find green algae colonies like these to be aesthetically very pleasing. There is something about the regularity of the spacing between each cell that appeals. Each colony consists of multiple genetically identical cells. Each cell is capable of surviving on its own and can reproduce to make an entirely new colony. That's what makes it a colony rather than a multicellular organism. In multicellular organisms, the cells need each other to survive, and not every cell is capable of reproducing. The cells of each colony are held together by a translucent gel-like filaments or a matrix. That's what gives them that wonderfully regular spacing. 

I found the first set of colonies living in the garden pond at the Wave Hill center in the Bronx, NY. The genus is Dictyosphaerium. The second set are from the Harlem Meer up at the top end of Central Park, Manhattan. The genus is Sphaerocystis. 

The pond at Wave hill

The Harlem Meer