Easiest way to get one? Want to go back under water to do seahorses

The seeds are dropped by all of the underwater wildlife, other than the mermaid (which only drops a toadstool seed the first time you spot her).  You can see how many you'd need for a seed in the Wildlife Guide.

Do chocolate eggs hatch underwater?

No, they don't :)

Tracey (hate to be a pest) if I have eggs, let's say a violet and red, how might I place them to give me a greater chance of the red chick coming out of a red egg? I seem to remember something about this.

I just replied on the other thread, Benni, but I'll copy it here too :)

(red eggs only hatch red chicks though).

You'd want eggs of the colour you want, plus the next colour down - so if you wanted to protect a violet egg to get a violet chick, you'd need violet and indigo.  Anything lower than violet would go to the indigo egg so if the violet wobbles, it can only be a violet chick/sea-horse.  If the indigo wobbles first, you'd dump the food (so you could keep the egg) and put out fresh to try again.

It works for all colours - so you'd use a blue egg to protect an indigo one for an indigo chick, and a green egg to protect a blue one for a blue chick, and so on :)

You're such an angel, TY!!