Traditionally moorings are a block of concrete with a steel rebar loop, dropped on the ocean floor and your chain attached to that.

I have an issue with the exposed metal rebar as your anchoring point for your chain. So my design of mooring block uses a pvc tube through the mooring block, that has a heavy duty chain passing through the block. The size of chain will be determined by the total weight of the entire mooring. The biggest advantage of this is that it makes the mooring serviceable; you are able to replace the chain as needed as a result of corrosion and wear.

The larger the boat, the larger the mooring needs to be. However if you need a 6000lb mooring the logistics of building it and transporting it to the location, while not impossible, get exorbitantly expensive. There are several mooring designs that use multiple mooring blocks placed in a fan type arrangement. I don’t know if that works anywhere in the world, perhaps on a rocky bottom, but I doubt it. Here in La Paz our boats do multiple  360 degree swings throughout the day with tide and current movements and this type of mooring just gets tangled. My design puts the 1300lb mooring blocks in a line, think of it as a train, with each 1300lb block chained to the next with a small space between each, small enough that there can be no tangles.

The next thing to look at is how to get the mooring block the settle into the sand as far as possible. Concrete is not a lot denser than the sand on the ocean floor is, so generally it will not bury itself deep into the sand. You also find that the weight of concrete decreases a lot in water. With my design we build the mooring block mostly with solid rock boulders, about 85% and then use concrete to bind these all together inside a plastic mould. This increases the specific density and helps the mooring block to settle into the sand a little deeper that just regular concrete. That wing said do not use this as an addition design factor, similar to design that screw things into the ground. Remember the storm force is a lifting force each time you bow is pushed up by a wave passing under it. So in my opinion the only secure criteria to design around is weight. So our 1300lb (on land) mooring block will give you 750lb of downward anchoring force in the salt water. So for my 26ft McGregor trailer sailor I use one mooring block on its fair weather mooring. I do not have that boat out on a mooring during a hurricane, it on its trailer under a storage shed. For S/V kwaai , 37ft Hunter, if I had to do a new mooring I would use two mooring blocks that is 2600lb on land and 1500lb in the salt water. I would use ½” hot dipped galvanized chain to tie the mooring blocks together and 3/8” chain all the way to the bow of the boat with a mooring ball that is theft proof for when I am not using the mooring.