I'm not sure there is one, but you can count the tiles. One thing that helps is to turn on the production icons, so that you can see the differences, especially with ocean and coastal tiles.
Coastal tiles will have 1 food, 1 industry, Ocean tiles have 1 food, 1 energy. There has to be 3 tiles between you and another settlement or station (so 4 tiles away) but if you are aquatic and moving, you can move to 3 tiles away to capture territory (aggressive), or to pass between 2 of your own colonies. Also you cannot settle on mountain, rift, crater, ocean or trench (no production) tiles. Once built, you can move colonies through ocean tiles (and finish movement there) if you have the tech that allows this, but the settlement must still be started on a coastal tile.

When doing aquatic cities, I decide where I want the center to be, then start the colony in a coastal tile in what would be the corner of the 2nd ring (two tiles from the center point). That way it only takes 12 moves (12 turns) to capture all of the territory and move back to the center, instead of 14. If you need to mark the center spot, you can send a ranger or Sabr to wait there, and they will become part of the city defense when you are finished moving. Both of those units can have a range 3 attack, so they make good defenders.

To get a movement per turn quickly: Build a new colony, send a caravan to boost production and food. In the colony, build a trading post for the first building. When trading post is built, buy a caravan for the city and send it to the best available internal route. At this point you should be able to move the city 1 hex per turn. If not, build a water refinery second (or purchase it). Build a Thermohaline Rudder third (or purchase it). Spend 12 turns capturing territory and move back to the center. When you finish moving, you will have around 8 population, a full circle of 3 tiles radius, decent production, and you can start rolling out defenses and the rest of the buildings. You may need to purchase Frontier Stadium (if you have it) and Rocket Battery to protect yourself if there is nearby conflict. You should still be able to move a hex per turn with those buildings with the production and 2 caravans running. You should also have workers developing the tiles as you capture them, so that when you are finished moving, the territory can support the population with or without the trade routes (2-3 workers helping each new city).

Thanks for the detailed answer (I would call it a guide, thanks). Count titles - do it (as in Civ 5). But I really liked the way in Civ 6 inaccessible titles are highlighted in red. Very mega-convenient. I'm used to it. It is a pity that this is not such a mod. Thanks again =)

Так, разве кроме гор, каньонов, океана и края карты есть места где нельзя поставить базу?