How to reduce the Loadtime of my "Epic Islands" Map?

Hey Guys,
my map runs really good, if there won´t be 1 Sublevel, named Underwater_Ls1…
If I start the map it needs about 1 minute to load all things in, but only the “Underwater_Ls1” needs 45seconds.

It´s a Rock-Formation (Link - You can find it between Skytropia and Isla de Canicula):

There are 268 actors and 1 LevelBounds (lights are only in the level for the screenshot).
I don´t think, the amount of actors are the Problem, because my first Cave has over 1000 Actors…

The upper Rocks has a “Max desired Draw Distance of 750000” (to draw them from a larger distance), maybe this is the problem?
But shouldn´t be the Problem, because in my Cave it´s the same…

Collision Presets is set to “Ground”
(with “Ground” you can swim under the formation without stucking)

Here are the complete Details:

The File has a Size of 736kb in the Folder, it´s one of the smallest…
(The Cave has 2164kb and loads in under 1 second, and there are not only meshes in the level)

I hope anyone can help me^^

Yeah, that´s the problem, everyone needs help, but no one want to help me…