Thank you to all that came; In the end I decided to summon near the Shrine of Justice, both for the proximity of easy resurrections, and the closeness of deep water. We went through 8 Fabled Maps, and the summoning was as follows...
Net 1: Leviathan
Net 2: Scalis
Net 3: Leviathan
Net 4: Leviathan
Net 5: Leviathan
Net 6: Leviathan
Net 7: Leviathan
Net 8: Scalis
The basic idea seemed to be a success; especially when Heimlich and a lady whose name I forget came aboard to help pummel Scalis from my ship with Heavy Cannonballs! Each hit took 1000-1100 hit points off him, and whilst the warriors etc kept aggro on the shore, he wouldn't normally come and give us a clawing... It also has the advantage that pets can stay at ranged to fire at him, and if he occasionally summons the snakes onto the ship, they can quickly clear the decks again. You can also escape aggro quickly by teleporting on and off the ship via the boarding ropes, and pets will auto follow you...
However, trying to get back to shore got increasingly difficult, due to a strange growth in the population of Sea Liches, living on the corpses of the waves before! Also movement on the ship itself becomes very hard with corpses on the deck; and what turned out to be a reward chest that I picked up thinking it was just more blocking litter, and left on the ground later... which Heimlich snaffled

And the RNG seemed to hate us, no one got anything... EXCEPT on the final Scalis, when Lanjar (He-Man) who doesn't even have the High Seas expansion, and I had to nearly beg to get to come along just for the sake of it... got the Small Soul Forge drop! Congratulations to you, you sassen frassen lucky git!