I have not been able to disembark units from a ship to tiles covered by tundra or a river. I tried other tiles (with grasslands and forests) and there was no problem. I am also able to launch "amphibian attacks" directly from a ship to lairs, caves, dungeons and towers. I haven't tried yet to disembark on a desert.

Is there an extra movement cost to enter certain terrain types from a ship that makes it impossible to disembark on them?

Yes, I am deselecting the ships. Perhaps it had something to do with moving all the stack at the same time (there were several heroes)? But again, I could disembark them on grassland without problems.

I don't know what to tell you. I just loaded up a save, built a couple Triremes and a Galley, threw some random units in them, and the units were able to land on a few different river mouths without issue. I didn't have any good tundra to try that terrain type, but I have no reason to think it wouldn't work too. I tried throwing 6 heroes and 2 rando's into a Trireme, and they all disembarked at the same time with no trouble too.

Do you want to post or email the save?

Actually, now that I think about it, what version are you using?

Master of Magic 1.3.1, offline installer from GOG, no mods.

Same version as me. Don't know what to tell you. :-/

Quick but important update: today I haven't been able to reproduce this issue. I took some units on ships and I was able to disembark them on both tundra and river tiles. So I'll just classify it as a weird temporal glitch.

Thank you anyway for your efforts on trying to find out what was going on!

Weird. Glad it cleared up, though!

I was thinking about this a little more. How, exactly, was the problem presenting itself? Were you able to have the units selected and ready to disembark, or were you unable to select some/all of the ground units as the ones active and ready to move?

During one of my tests, while moving a boat the units (two dwarf engineers) on it apparently had their movement allowance for the turn used up. They weren't able to disembark that turn as the boat finished moving adjacent to land (I couldn't select them to move at all, as if they were out of movement), but they were able to move off the boat next turn.

At first I thought too it would have something to do with ship movement points, but after getting them next to the coast I waited quite a few turns. With the ships stopped, I was still unable to disembark the ground units (which I could select).

1) The map is effectively a cylinder. Were you trying to disembark on/near the wrap-around point, where the left side and right side connect?

2) What units were you trying to disembark, and from what kind of boat?

3) Did any of of the units have Plane Shift capabilities? Shadow Demons have it innately, and I think there's an item that can give it to a hero.

4) Did any of the units have flying or some other mode of overland movement that was imparted by an outside spell? For example, Water Walk spell cast on a normally land bound unit.

5) Were multiple boats in the stack?

The game is already wrapped up but I'll try to remember:

1) No, but I was very, very close to the Northern edge of the map, if that matters.

2) The fleet was composed of triremes and warships. My units (a mix of Halflings and High Men) were swordmen, slingers, shamans, catapults and heroes.

3) No.

4) I did experiment with a Water Walking spell, but I ended up putting that unit on a ship because it was faster anyway. I don't remember if it was part of that particular army.

5) At first they were, so I separated them, with no change. Only when I moved them and ordered the units to land on grassland/forest it worked.

I'm assuming you weren't trying to do anything with or on the northern-most map border, what would be the North Pole or whatever, since the terrain is worthless for pretty much everything, so that shouldn't be an issue. I know the game can get a little goofy in certain scenarios when you are doing things on the borders of the map (for example, raising a volcano next to water right at that East-West connection might cause a tile of water to turn into land).

The only units I see in that mix that might have even vaguely been the cause would be warships (as boats that have no transport capacity) and heroes (because they have so many options for game mechanic interactions).

Oh well. I have no new ideas, so I'm back to writing this off as one of those rando one-off goofiness things that occasionally occur in this game.

According to the unofficial 1.50/1.51 patch, there were bugs with the game's pathfinding that would sometimes happen:

Completely rewritten way to find paths on the overland map for moving units - original sometimes caused units to be unable to enter map cells they should have been able to, like units being unable to leave a ship. (371, 411, 489)

https://masterofmagic.fandom.com/wiki/Unofficial_Patch_1.50

Thanks for the info!

I will have a look at that patch. I like that it fixes bugs, but I am not too keen of fan-made balance/gameplay changes.