A default transport_ship has (small) naval-def 8.
A pt_boat has only nav-sml atk 1 and does 4 damage to a unit that has just embarked.
A pt_boat_42 has nav-sml atk 2 and does 8 damage...
pt_gunboat has nav-sml atk 3 and immediately sends the transport to Neptune.
This is totally in contrast to an idle naval transport that started the scenario in the water and hasn't moved at all:
pt_boat: 0+ damage
pt_boat_42: 0+ damage
pt_gunboat: 1 damage
No mercy to amphibious retreats?
