You can lay the
boat up on a soft bottom if you have a significant tidal range. The
boat will either lay over on it's side as the tide drops or sit upright if the bottom of the
keel is flat. Did it once with the boat upright in Charleston. Ran anchors out either side and attached them to halyards to keep the boat upright. Don't know if the halyards really held the boat upright as it seemed to be very happy sitting on the flat of the
keel. Have laid the boat on it's side more times than I'd like to admit running aground. FWIW, purposely grounding a boat to do
maintenance is called careening. Before the days of travelifts and/or abundant
marine railways, it was the way that boats were maintained.