Luminescent Research Notes

Luminescent Research Notes are obtained by bringing one or more of the following luminescent creatures to Edgar Fish 'N' Sea in the Scalding Chasm in the Abyssal Depths: The rate of notes obtained triples if one of each type is brought to the sub. From then on, until the creatures stop following you, it's just a matter of avoiding the Whale Shark by turning the light on the diving helmet off and back on.
 * Luminescent Eel
 * Luminescent Grouper
 * Luminescent Jelly

As a currency

 * Damaged Diving Helmet (item)