Sea-faring amongst Lizardmen is an interesting prospect, whether it be from a perspective of using some of those beautiful stone ships as shown above, or the more basic idea of strapping howdahs to sea-going animals, such as this old chestnut of a custom model.
Total War Warhammer 2 also cites the existence of Pliodons, "large, river-going creatures that seldom move on to land. They are used by the Lizardmen to ferry cohorts across bodies of water."
Interestingly enough, Pliosaurs were a type of marine reptile present during the time of the dinosaurs on our world, the most famous of which being the Liopleurodon (massively upscaled by Walking with Dinosaurs, but quite a beautiful prospect for a model)
What it comes down to is, I think a matter of interpretation and common sense. Large aquatic reptiles tend to swim below the surface, which while it would offer the Lizardmen a uniquely stealthy and deadly living submersible fleet, for Saurus not blessed by Tzunki, would be quite an issue, unless the guide for this mount was ensuring it remained surfaced. As a result, it seems likely that such beasts would be used for short range crossings, or if used with aquatic troops, might be used as transports similar to how Navy SEALs and other special forces use submersibles to deploy troops undetected, with a bonus of a large sea-faring monster providing support.
Long story short:
- Short Range Crossing: Aquatic or Amphibious Animals (preferably reptiles)
- Medium Range Crossing: Stone Boats or Temple Ships
- Long Range Crossing: Site to site teleport across the Geomantic web (But only if there is a viable link on both ends)
- Exodus into space: Bigger Stone Boats. Kind of.
So, to establish teleportation, the First need to be in control of both locations, and to travel further afield.
