I had a thought earlier, and i think it would most definatley be in keeping with the mod: Diving gear
The basic model would be Scuba gear:
Which you could use to explore rivers, and perhaps the shallower parts of the ocean.
The second idea,which is more advanced is this:
This is an Atmospheric Diving Suit (ADS).
With it equipped and on the land, you'd walk slower, perhaps as slow as moving through soul sand. Obviously you'd need to include some machinery which will generate the gasses required for your character to breathe while you're underwater.
and no more Efficiency 3 on my nano saber for leaf cutting :p