This question concerns the Amphibious Enchantment (covered here) and its benefits to mermaids (covered here). Why? Number one, because the monsters I call Snappers will be quite available in the ocean (and by extension, their Enchantment) and number two, because moving on land with a fishtail is quite difficult.
The basic benefits of the Amphibious Enchantment are three, and I'm listing them here:
Hydration-Mermaids can breathe air and water in my setting, but they don't stay on land for long; being out of water for just two hours turns a mermaid's skin and scales into an inflamed, cracked, bleeding mess. Amphibious mermaids don't have that problem and can stay on land indefinitely.
Movement-AKA being able to move in water faster. The Amphibious Enchantment would enable a mermaid to move in water with the same drag she'd experience in air, therefore enabling higher speeds overall. This same effect makes Snappers surprisingly fast in water.
Riding-Mermaids and humans have a certain agreement, in which people use boats only when necessary and mermaids transport people the majority of the time instead, usually in exchange for money, jewelry, or other valuables. This is quite lucrative for mermaids, and a mermaid can carry an Amphibious person in water a lot easier than a regular person, and for longer (as Amphibous people can breath underwater).
However, if a mermaid maxes her Amphibiousness by killing or eating twelve Snappers, she becomes a Skyswimmer and can A) swim or float in air like it's water and B) turn her fishtail into legs.
This opens up a whole slew of opportunities; regular mermaids can swim down to the bathypelagic zone without being negatively impacted by the dark or cold down there, and Skyswimmer mermaids can reach equivalent heights on the surface, potentially allowing them to "swim" over mountains and even buildings without a problem. Obviously, Skyswimmer mermaids can also interact with humans a whole lot easier than regular mermaids, and they can also be paid to carry people around like a personal taxi (which will likely become some kind of expensive status symbol).
My question is, how beneficial would the Amphibious Enchantment be for mermaids?
Specifications for Best Answer:
The best answer will first account for and analyze the benefits of Amphibiousness, such being able to stay on land or in dry areas indefinitely without becoming a bleeding mess. This need not be an exhaustive list, just cover the most useful/impactful/lucrative applications.
The best answer will then account for the benefits of being a Skyswimmer for a mermaid, including A) the benefits for possible human interactions (trade, manipulation, and so forth) and B) potential career paths and C) useful implications.