I've looked in here a few times but never contributed before.
I think the derivation of 6D is that "sandy" is "buff", as in the colour, with L(ost) inside.
I knew a manatee was a sea cow but I was racking my brains for how it came from dinghy carrying each... then I discovered that a scow is a flat-bottomed boat.
I only got the RT yesterday and, if I finish the crossword at all, it usually takes me a few days.