You have to look at the strut....the twin strut pictured above has flanges on each leg...undoubtably, hiding behind the flange will be some bolts.
The bolts go thru' the hull, the flange will bear on the hull bottom, and the bolts will be tightened with a nut inside the hull.
A single strut typically goes through the hull and is supported against sideways movements inside the hull by various methods depending on the manufacturer. When you see a single strut there is likely as much lenght inside the hull as what appears outside the hull.
A single strut is typically quite substantial, it would take some force to mover or bend it.
My guess that the V-strut above, is likely for a power boat
. The legs are not very long.