The captain gained the standard bonuses that an ancient devil fruit gave such as an increase in attributes and a tougher body but other than that there was no real difference without him changing forms. while the changes interested alastair the biggest change was the one that interested him , the inability to swim or touch sea stone. using his powerful senses including his magical ones alastair noticed that a foreign energy had entered the captains blood stream and was spread across his body. as an experiment alastair dipped the captain into the ocean and figured out what the curse of the fruit was really.
It turned out that the energy froze when a fruit eater was surrounded by water and because this energy was in the bloodstream it prevented and energy from reaching ones muscles. this meant that the weakness was actually similar to musculature asphyxiation. for the those not in the know this is when no oxygen is reaching ones muscles causing them to cramp up and fail to work , this would explain why devil fruit eaters grow weak when exposed to large amounts of water. as for sea stone alastair theorized that the thick water energy the stuff gave off worked on the energy the same.
If any of the world elders were to hear this theory they would spare no effort to hunt alastair down as he had solved a problem even vegapunk hadn't figured out. this wasn't to say that vegapunk was not a genius just that he lacked the ability to sense the mystical energy clearly unlike alastair. with this knowledge alastair began to experiment with his fun sized forge to try and make a reverse sea stone that would allow those who ate a fruit to swim and use their abilities underwater.
Needless to say alastair had no intention of spreading this discovery because frankly the water weakness was the only thing that made devil fruit manageable. if the biggest weakness of them were suddenly removed the fruit users would need to be killed rather than imprisoned since no prison could hold them at that time. for all the flaws the marines had working for the world government most of them truly worked to maintain world order and alastairs discovery would increase the difficulty of that immensely leading to a huge increase in innocents suffering. this wasn't to say that alastair was going to join the marines or any such foolishness.
After experimenting for a week alastair created a suitable material that while it didn't remove the entirety of the effects of water and sea stone it only returned the user to regular human standards but still allowed for movement in water. this was perfectly fine for alastair since most of his abilities would not based on a devil fruit even if he got one he liked. after making enough of his land stone as he called it for himself and his wives alastair spent the rest of the trip to logue town relaxing under the sun.
The ship arrived near logue town at which point the crew began the procedures to dock there including taking down the flag before the marines could see it. this turned out to be a wise decision as when the town came into sight a huge amount of marines going about their business could be seen at the docks. the crew docked the small ship in an open spot which was admittedly quite hard to find before alastair gave the crew the promised payment and wished them well before leaving with the girls. who looked around in awe.
Logue town was similar to how it was depicted in the show with many tightly packed multi story buildings made of a grey stone and flat roofs made up most of the town. a single building set high on a hill overlooking the town was the the exception as it was made of a white stone and flew the flag of the world government proudly. the group headed over to a nearby treasure shop , which was a place that existed since it was common for people to suddenly find treasure left by either a pirate or someone else.
Alastair traded a good amount of gold ore for about thirteen million berries which is the currency of the one piece world. after leaving the shop much richer than before alastair went sight seeing with the girls. obviously they went to see the execution platform where gol d. roger was killed after alastair explained who that was to the girls as well as the effect he had on the world. after paying their respects to the legendary pirate they went looking for any interesting thigs they could find in the local shops. alastair noticed the cursed sword that zoro eventually obtains latter but leaves it be.
In the end alastair bought a guide to all the famous swords as well as a map of the entire east blue in great detail. the girls bought little souvenirs of little value with the exception of jade who bought a new spear that seemed to call her. it was a black handled spear with a silver swirl going down its length but it head was the really interesting part as it was seemingly made in a similar way as a katana.