Aquatic creatures and reach

[RavensLand]

I'm simply trying to work out the mechanics of a large-sized, swimming creature trying to fight people on a ship.

For example I'll use the giant octopus: it is large sized and has a 15 ft reach.

If it came to the surface would its reach begin right at the surface, reaching 15 ft straight up, or could it feasibly be half out of the water to reach up 20 ft?

Are there any rules in the DMG or MM I've missed? It seems like a niche thing that wouldn't come up often.

[Finback]

If it came to the surface would its reach begin right at the surface, reaching 15 ft straight up, or could it feasibly be half out of the water to reach up 20 ft?


In my mind, the issue is *how is it half out of the water*? If it's floating on the surface, generally an object will remain there. If you're in the pool, floating, and reach your arm up, you can't really elevate your body out of the water (for long, at least) to keep that extra reach. However, if you're suggesting it climbs onto a rock, or slightly up onto the shoreline, then it really just has its same 15ft reach, just from further up the shore.

If it's on the shore's edge, it can reach someone 15 ft up the beach. If it crawls five feet, it can grab someone 20ft up the beach, since the net distance remains the same. But a creature on the surface of the water has nothing to move onto, to get that extra five feet (unless maybe it surges like a dolphin for a second).

[Ninja_Prawn]

It's an interesting one. I'd allow a large (i.e. 10x10) creature to have it's body halfway out of the water, I think, giving it reach up to 20ft into the air.

In the one encounter (http://www.giantitp.com/forums/showthread.php?475390-A-Faerie-Affair-IC-II-A-Pixie-in-a-Bottle&p=20912648&viewfull=1#post20912648) I've run where this was relevant, though, the creature climbed up onto the PCs' boat, so I didn't have to grapple with this particular question. Get it? Grapple - like a giant octopus? Gah, my genius is wasted on you people.

[hamishspence]

I'd also allow Jump checks to see if the creature can contact something some way above water, for Charge attacks - thus, a water creature can charge vertically and reach something quite a bit out of water.

[Maxilian]

Well why not grapple the ship 5 feet over the water?
https://i.kinja-img.com/gawker-media/image/upload/s--oEzAtsgV--/c_scale,fl_progressive,q_80,w_800/fadgyabi3efhqqcuns7s.jpg

That will make you stay at that certain height and that basically means you get the 20 feet (kind of)