Con 20 and bump Cha to 5.![]()
I think we should keep Indefatigable Swim but perhaps alter it slightly to give it a larger than usual carrying capacity.
EDIT: on the feats, let's definitely drop Weapon Focus and give them Endurance and Toughness as the normal feats.
I've just spent more than an hour paging through a variety of Dragonlance sources to try to provide a firm answer to this question, but it seems that the ferry turtles are only mentioned once, in The Sylan Veil, and that doesn't specify how many pull each barge.I'm unsure as to how many turtles pulled each ferry. It could have been several per barge.

Yes, let's go for Carrying Capacity option 2.
Alertness seems like the most appropriate of those feats.
I'm fine with the 75% fortification and 100% when withdrawn. These are magical critters, after all, and they just seem like they'd be tough.
Looks like we need 200 rounds/20 minutes for Hold Breath.
CR 4? They seem to fall in between the juvenile and adult tojanida, which are similarish critters.
I think they probably shouldn't get any bigger. They were magically enlarged in the first place, so it strikes me that their default size should be the largest they get.Will we have them living in groups? I like the idea of them being social beasts.
Do we want them Advancing to Huge size, or will we keep them Large
I think they probably shouldn't get any bigger. They were magically enlarged in the first place, so it strikes me that their default size should be the largest they get.
I'm also not sure they should be social beasts, since the only examples were bred in captivity and are used as beasts of burden. Then again, they might have retained social traits from their original forms and indeed live in groups when not put to work pulling barges.
This is the problem with the somewhat uneven CR system. There is a pretty big difference in damage-dealing potential between the ferry turtle and ogre, but, as you say, the turtle's defenses are much better, including quite a few more hp. Plus, it lives in the water, which is a little tough for most PCs of that level to deal with (given the good defenses, ranged attacks would take a while to do too much to them). Meanwhile, it's much better than the juvenile tojanida. And I'd say it's comparable to the CR 4 sea cat. Maybe this is a case of the ogre being under-CRed? Anyway, I'd prefer CR 4, but I don't think it makes a huge difference, as these shouldn't be targets most of the time.
Turtles are pretty social in my experience, in as much as they hang around in fairly large groups as often as not, even if they don't really interact most of the time. So I'd think a group organization of 4-20 is reasonable. One noun for a group of turtles is a "bale"; how about using that?
I recall the ogre being under-CRed, so that's probably not the best creature to use for comparison purposes. But I'm really not good at judging CRs at all -- it's been far too long since I ran any 3.x monsters.We seem to be at an impasse, shall we turn to Echohawk to decide?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.