I am new to supping and what to wear when the temps are in the 60’s. It is not if I fall in but when I fall in, as it is inevitable.
60F water temperature or air temperature? The water temp is the most important.
You don’t mention where you will be paddling - Rivers, lakes, ocean? Most people invest in wetsuits for paddling sup in cooler weather. When the water gets down below 60F, you need to have a wetsuit to protect against hypothermia. For surfing usually a 3/2 suit works for water temps from low sixties to around 57 F. a 4/3 suit works for water temps 57 -50 degrees. It does not sound like you are going to be racing or extreme fitness paddling, where a wetsuit may be an issue. If you get too over heated just fall in and climb back on. If you are a beginner probably not a good idea to be paddling off shore or in challenging conditions in water temps below 50F, even with a wetsuit. Find some experienced paddlers in your area and gets lots of ideas of what the best paddling clothes are for your conditions.
It is not unheard of for someone to paddle a SUP in a dry suit, the same type that a kayaker would wear.
SUPs could involve a fall in, but have the benefit of generally being much quicker and easier to get back on the board from a fall than a kayak. Assuming you are one of the many who can do this (please test to make sure, before it becomes a life threatening assumption), then with that fast recovery/exit from the water you can often get away with non-immersion clothes, but clothes that keep you warm when they are wet. So much like what you would wear on a hike in the rain.
If getting back on the board is not something that comes easily for you, then wearing immersion clothing, like a wet suit or dry suit, may be in order. Immersion clothes should be based on water temperature, not air temperature.
For added safety, you should always wear a leash and PFD.
For someone starting out I would err on the side of using immersion protection if the water temps are below 60F. There are a large number of deaths occurring with inexperienced SUP paddlers falling in and finding out about how quickly cold water can incapacitate someone. I’ve seen SUP paddlers use drysuits in extreme conditions, but the average dry suit is not very aerodynamic. Something that is much more important than for kayaking. You want to have minimum wind resistance when SUP paddling. I just got back from a trip to Sweden and saw 0 SUP paddlers wearing drysuits on cold water. The ideal is warm water and sunny temps and you can just use conventional board shorts and rash guards etc. For someone starting out check what local paddlers who teach SUP are wearing on your water conditions.