Loading a vessel in water destroys the vessel

[Aelipse]

Heya,

I've playing with submarines lately (using the fantastic Otter mod by RoverDude), and I found that if I approach the submarine with another vessel and get into the loading range (2.2 km), I get the "vessel is destroyed" message and the submarine is no more. I tested this while having the submarine both at the bottom of the sea and on the surface, and the result is always the same. Is there something I might be doing wrong, or some clever way to prevent this? I am playing on 1.7.3. Thanks!