Adding my 2 cents, I didn’t buy the chest, and you will get one (and the shipwreck) as prizes at the end of part one. The chest does drop shells, but they are a semi rare drop. Better to chop anemones. Collect from the castle, mermaids and the pet nagas as often as possible (the plain “naga” ones) if you have any. The nagas and the castle can drop anemones and reefs. And Sirene has actually dropped ready made mermaids brew a few times!
I am now 5 silver bars away from completing the last two gold tridents to complete the tide pool! Then I just have to fight Heska and build a prison. We sure are tossing a lot of stuff into that tide pool. I keep hearing Ariel singing “Look at this stuff, isn’t it neat? Wouldn’t you say my collection’s complete?” But I fear it is not....... I just hope part 3 (if there is one) calls for some new crafts using all those marmosea drops and NOT mermaids brew, storm water, and silver bars. Sigh.