Walt is on the right track.
If you want legs, the only commercially available ones I know of are Yacht Cradles - Yacht Legs - Boat Stands - For Sale - The Yacht Leg & Cradle Company
. In many areas of substantial tides there are seawalls or docks you can tie up to at high tide that dry out at low tide.
Careening per se means anchoring or otherwise tying up the boat so it settles on its side when the tide goes out. That works best where there is an area of soft bottom where the bottom is relatively flat and dries at low tide.
It all works, recognizing the quite appropriate comments above about environmental impact.