My thoughts also.
Re mud: Mud offers less friction but it has a nasty habit of “sucking”.
In 1992 had experience of sitting on mud in English ports on coasters /minibulkers. We got this clause in the charter party called NAABSA- not always afloat but safe aground regarding some ports. In such ports vessels sit on the muddy ground during ebb tide.
The vessel simply sits flat on the ground and when high water comes it refloats . But it is not an easy experience. Ships are given by the port special strong lines, as ships lines are not of sufficient strength to withstand the " lift off " experience once the vessel releases itself from the ground .
And it stays there longer then one would expect due to regaining of buoyancy as the ship is “sucked” to the ground and the water needs to rise much , much higher to generate the extra buoyancy in order to unglue the ship from the ground.
I thought once that our decks will be flooded with water -so high the water came and then…explosion and lift off. We were sort of catapulted vertically. The experience is unbelievable. And this powerful suction is caused by…sticky mud. So even if dredgers clean her sides , still her bottom will be sucked with a powerful forces which may be difficult to calculate as she did not settle gently on the mud but burrowed/ploughed herself into the mud with tremendous energy resulting from her speed and mass.