Mission 6 help needed

[Woland]

Sorry playing locolized version of the game so names and titles might be somewhat out of sync.

This is the 6th mission, right after the Resistance. I think in english it be called "Chilly Reception"

The bonus objective is to sabotage a gunboat. I can see on the right side of the boat a green glowing TNT pack, so I assume it works like in earlier missions - you just get close to it and click F (or whatever you have for "use")

However it doesn't work simply because i am in the water and cannot reach the damn thing. What am I missing?

Thanks in advance.