Practical Sailor has published information on what to do if the water suddenly recedes. Do any of our members have any experience with tsunamis? During Hurricanes Irma and Maria, the water receded in several island not because of tsunami but because the storms were so powerful they pushed the water ahead of them, sucking it out from behind them. These are very different phenomena that require different approaches, neither of which is predictable.
Vice Commodore, OCC