Sea Shards: I don't agree with the sea shard idea because some people have like around a 100 or so sea gens and people can afk with a massive storage to stockpile sea shards. Even though 1 in 100k is extremley rare, being able to afk with even a small amount of sea gens can allow you to get a good bit of shards which you can invest, and eventually make a monopoly off of. This would for obvious reasons break the economy so I don't think it will ever get added.
Sea Hearts: I don't think there really is any point in having this because you can obtain sea hearts so easily through playing the minigame repeatedly so its kinda useless to just have a chance for sea hearts to drop.
Sea Lion: I agree with this idea, I do think that the sea lion should be buffed a little bit because it takes so long to fish a sea shard
I hope my feedback wasn't too harsh and that you understand.