lol ill tell you guys.
you would think the mussels are random. and many times you find them doubled up in a spot.
well some spots they tend to commonly spawn in pairs, and often, even if you boat back and forth they can fast respawn.
i figure its just a sweet spot where grids line up and the randomizing formula is just goofed.
i see one of these spots every now and then. i made a house right in front of one of these spawn stretches. and slapped a char and cauldron in it.
just go in and out of the house over and over, and nearly every other time i step outside there are 1 or 2 respawned mussels.
pearls are just as horribly unlucky, but i get 100 mussels in 5 minutes now.