I suppose this can be reported here because smarter equip mod is shipped with OXCE.
If I enable smarter equip mod with TWoTS, many early-access items of 'categories: [STR_DUALENV_WEAPONS]' disappear from the equipping screen regardless of the starting conditions (underwater / surface). Tested with OXCE 7.13, I haven't tried this earlier.
You can test this with, for example, a new battle with Gas Cannon or Magna-blast grenades. For some reason (not inheriting anything from vanilla definitions?), for example ADS works.
However, I'm not sure if 'smarter equip' is even supposed to be compatible with non-vanilla TFTD (and more precisely, what kind of mods will cause misbehaviour). But if it isn't intended to work, I wonder if there should be some way to mitigate confusion like this.