Hi Mistral. Is there anywhere close to you with a sloping beach. Take a leaf out of the book of Matthew Flinders...When his Endeavour was rotten and leaking. he beached it for repair and would have had to lay it over to get at the side...Is it possible for you to get some help and do that. Even if the daggerboard is sticking down two feet, you might be able to get it into water shallow enough to have a look and suss the problem...Otherwise, do you have a big blue lifter in the area...say at a yacht club. They can sling it and direct lift it out.
Not sure of this, but can the

daggerboard lower out the bottom if you release the safety rope?. What does Roger say?
Come on Rog...some help here...Puggsy 06
oops...should have read the other comments first....sorry guys!.
It does come out the bottom.
p.s. No sharks in these waters...the crocs have eaten them all.