The first thing that comes to mind is if this is a feeder to a panel that will eventually have pool equipment branch circuits... the feeder must be ran in a compliant conduit not a cable like nm-b. Best would be thhn/thwn individual wires in PVC with an insulated ground sized to table 250.122. If the pool is not going to be heated a 60 amp feeder should do you just fine from the description of what you will have for branch circuits to equipment at the garage. The equipment ground for 60 amps would need to be 'minimum' #10 copper. The two hots and neutral need to be #6 awg copper. The neutral by code needs to be white insulation along its entire length, the two hots can be black. If pvc you need 1" to have ease of pulling for a 60 amp feeder. No more than 360 degrees of bends before a pull box or termination point. Stay away from sharp 90 degree fittings use sweeps when at all possible. Your neutral and ground at the sub will be kept serparate ( study the attached diagram) this is accomplished by adding a ground bar kit and not installing the bonding means to the neutral bar of the panel. This is usually a green screw that threads into the panel metal after inserting it through the provided hole in the neutral bar.
If you wish to have a disconnect I would just get a 100 amp main lug sub panel that will accept a back fed double pole breaker of 60 amps. You will need to also buy the hold down kit for the breaker since its is going to be a main. You would connect to the breaker with your feeder hots (backfeeding it) to energize the panel. You would not use the main lugs. Neutral of the feeder to the neutral bar and the equipment ground of the feeder to the ground bar where you will also connect all your branch circuit equipment grounds. Connect all your whites for branch circuits to the neutral bar in the sub panel.
Or you can just buy a 100 amp panel with 100 amp main breaker and feed it 60 amps of capability. It will then just be a disconnect and the 60 amp breaker in the house panel will be the overcurrent protection for the feeder and also used to remove power to the garage for emergency or other reasons.
Or you can just use a main lug panel (no single throw disconnect at the sub) and use the 60 amp breaker in the main house panel for feeder overcurrent and short circuit protection and to remove power from the sub panel in the garage.
You can also run a 100 amp feeder to the garage with a #8 minimum equipment ground and minimum 3# copper thhn/thwn unless they allow #4 copper locally. If pool is heated you probably will need this minimum and the service to your house will need to be capable of handling the load...ie..if 100 amp service to the house you can forget heating the pool....
... till you get a bigger service.
As an added note you can if you want protect #6 thhn/thwn in conduit with a 70 amp breaker...60's are common at the big box stores 70's not so common. You are allowed to do this because #6 thhn copper is 65 amps and there is no 65 amp breaker so you can move to the next standard size which is 70 amps.
Please use the below diagram for reference and as a guide...remember your going to be having pool branch circuits eventually from this sub so there is a long list of code requirements when doing that.. so bone up on the things you need to know for your families safety.
I've also attached a diagram of a Homeline 6 space 12 circuit panel that accepts a backfed main to give you a heads up on familiarity with doing that if you so choose.