Spell/Effect to allow casting underwater

[Tellus]

@Jonathan.Link

For example Covenants has Eternal Repitition in a Bottomless Pool, which could potentially allow two people to benefit from the same book simultaneously.

I don't see why this is a problem? Infact I bought an item with this effect for Titus specifically for that purpose. It's all according to the rules. That's not really problematic. Spells and effects that do not, are.

Hermetic Projects has Conjuration of the Seaworthy Cog, which uses the Target:Structure incorrectly, but I believe the level ends up the same, when adjusting it to T:Ind and increasing the size to an appropriate multiple.

Structure is infact the most appropriate Target for that spell, as Structure specifically includes the structure itself (as opposed to Room), and a cog consists of multiple obejcts.