Just a few thoughts...
Not letting police search the boat makes me lean towards there is something there. Who would go through all this hassle from the press if they could easily put that issue to bed? I'm not buying that he doesn't trust police - he could have an independent representative present during the search or set up a camera to record it. So I think it's likely they did go back to the boat, UNLESS it's just the dinghy he doesn't want to be searched. Perhaps blood evidence. OR - it's the anchor alarm on the boat that shows no digital record of going off. Her phone was on the boat, suggesting she did get back there.
Not contacting the coast guard when advised to do so by police at around 2:30am, makes me lean towards there was nothing to see there, at that time, in the immediate vicinity of the boat. Absence of evidence is evidence too. So I think it's likely Sarm was taken out to sea and is not on land.
Why would he be comfortable with a land search by police if foul play is involved and he knew she was on land? Without a means to move her body very far on land, she would have been found near the harbour/beach, imo.
Why contact police at 2/2:30am if whatever happened (assuming there was an event) only just happened and there is still time to find her? He doesn't know if police will contact the coast guard, he only found that out after speaking to police.
What's the significance of the anchor alarm? If it had gone off at 2am and that was when you discovered your partner was missing you would be thinking the two were related. Too coincidental for it not to be. Would you a/ phone it in to police and leave the boat to go ashore to meet them, make a record of a missing person, or b/ get in the water, muster help, and search for her, because the anchor's just been moved by something? If this was foul play - I lean towards 2am being the safe time to phone police, because 'the evidence' has been hidden already. There are 4 hours between leaving the restaurant and phoning police - say 1/2 hour on boat, an event precipitating the disappearance, 1 1/2 hours out to sea, 1 1/2 hrs back, 1/2 hour to tidy up in case authorities keep you busy and you don't get another chance and to come up with a reason one is awake at 2am. An alarm. Why not wait until morning to 'discover' an empty bed? Perhaps one thinks the sound of the dinghy (looking for her, but really returning) has been heard by occupants of neighboring boats, and you will have to account for it being seen out just before calling police at 2am.
One more thought about her phone being on the boat - it might have been overlooked during a panic; had it been taken out to sea it might have given a ping to narrow down a search area (do phones ping out at sea?); it might have been considered as too hinky for a person falling off a boat to have had their phone with them?
MOO
But the DM consistently has the best photos for these cases, and I do appreciate that we can discuss their info on this forum, because they sometimes cover info that MSM won't touch. 
