Gluing rocks underwater as securely as possible

[jeep and goose]

Does anyone have suggestions to get this rock scape super secure honestly the e Marco I got didn’t work well, I have stuff as tightly locked together as I can rn

 

[Mr. Mojo Rising]

I haven't tried e marco, I've tried the nyos and caribsea brands and both work well for me. However what I do, and what I would suggest for a large structure like yours, is I drill into the rocks and insert small acrylic rods that act like rebarb, then cement the joints together.

Honestly I don't know of any way to get it done underwater. But what you have looks fantastic, I really like it, I hope it works out for you, good luck

 

[exnisstech]

I've heard of people glueing under water but all I've ever done is make a mess when I tried. I can't even glue a frag while it's under water. The e Marco cement will create a bond stronger than the rock itself but I've only used it outside of the water and let it air cure.