Yeah, it's not really related to Admirals, but they're kind of just the default option for anything naval (i'm not at a computer right now, but is there still a free one in Commerce?) And I see what you're getting at, but, say the ability works like a ranged attack so you can get the canal to where you want it to be on land, is there any reason you couldn't just daisy chain admirals (never thought I'd type that) until you're where you want to be? I feel like if you could just keep building canals you could do some pretty trolly things with them if you had the gpt to support it. With it attached to an admiral, each single tile canal is a commitment, and if you want to make something longer you'll need to use your navy enough to justify it.