To give a bit of background and ground the question in context:
I'm concerned with the technology level from prehistory to Renaissance, or thereabouts. Analogous to Earth history, the 'normal' land-based species have already developed fully-rigged, square-masted ships.
However I also have an amphibious species that thrives equally well on land and in water (sea). They are based on a large archipelago with a lot of natural defences (straits, shallows, reefs, etc.). Their native islands are rich in natural resources in terms of ore, wood, and whatever else would provide the materials for conventional sea-faring tall ships.
My question, therefore, is what kind of ship designs would such an amphibian species develop? For my part, I've considered the following:
- Primarily only serves as a means to carry more cargo, as the species doesn't need shelter / protection from the sea
- Probably has some kind of 'anchor' points for the sailors that operate it to stay attached to it, so when they're sleeping in/under the water they don't drift away from the ship
I've also considered the wild thought of some kind of submarine thing instead of a 'ship' per se, since drowning wouldn't be a concern (although goods would still get damaged). I'm not sure what kind of propulsion system this would employ, however.
If it impacts the answers at all, there is limited magic in the setting, but it's quite expensive (think blood, sacrifice, etc.) and tends more towards adjusting already extant possibilities in the world rather than 'conjuring' completely supernatural effects or events.
I'm also happy to clarify further or add info if this isn't enough.
Thanks in advance for any help, this one really has me stumped, as I'm not at all inclined towards engineering or anything like that.