Back in the Victorian era, this was apparently a popular hobby. From Collectors Weekly:
Affluent Victorians often spent hours painstakingly collecting, drying, and mounting these underwater plants into decorative scrapbooks... Part of the appeal was what a seaweed collection said about the collector. Anyone could appreciate and collect flowers, but painstakingly obtaining, preserving, and mounting seaweed specimens demonstrated patience, artistic talent, and the refined sensibilities necessary to appreciate the more subtle beauties of nature. Queen Victoria herself made a seaweed album as a young lady.
And yes, the seaweed did smell bad. But Collectors Weekly reminds us that the Victorian era was "a more pungent time."
Back in 1936, Patricia Salter had an unusual hobby for a 12-year-old girl. She collected dirt. Whenever I come across stories like this, it always makes me wonder what became of the collection. I'm guessing that at some point it must have been tossed in the trash, or dumped outside.
But it looks like there are some like-minded dirt enthusiasts in the present day, over at the Museum of Dirt.