I use a Nissan Elgrand minivan / people carrier to tow my boat, it's a JDM Jap import so not a very commonly seen vehicle, 3.5 V6, it's a bit marginal in terms of power but does the job OK. Most people would assume it's 2wd and most of them are but this one has switchable 4wd, just nothing to say it has 4wd on the outside. I've never needed to use 4wd on a slip but do need to use it on our driveway which is a fairly steep hill going out up to the road and some gravel near the top just before the road. People see me launch with it at some places and seem to expect it to spin the wheels, it doesn't, plenty traction even without using 4wd.
Most slips I use are fine with a decent gradient but the slip I use at a place in Wales starts with decent gradient near the top then shallows off towards the bottom, so if you want to get out as soon as possible on an incoming tide you need to launch at the bottom of the ramp where the slope is too shallow. Dad used to launch at the same ramp years ago but he used ropes/chains so the trailer could be deep enough without dipping the back end of his vehicles in the salt water. Later he and his friend bought an old farm tractor for a £couple hundred to keep at the launch site and didn't worry about getting that in the salt water. Problem was it was only a small 2wd tractor, back tyres might've been 4ft diameter but they had less grip on the concrete than an average car despite having a pedal for difflock on demand, you could just spin boat wheels. Dare say that if the tractor had road spec tyres it would have done better but not with the usual spec mud tyres it came with, not sure if they make road tyres for farm tractors. When I last launched in Wales I did back the rear end of one of my vans right into the salt water up to near bottom of the tailgate level, I need a better plan for next time I launch there but at least when I got home I got the car up on a ramp and thoroughly jetwashed it underneath, have since undersealed it again underneath. I don't like shallow gradient ramps though.
A ramp might start dry but if someone has used it before you it will be wet anyway from the water that comes off the trailer and its tyres when they pull it out. If concerned about traction it might be a good idea to try to be the first to launch lol.
