AIVDM/AIVDO other altitudes
"Table 39. Site location payload" for record type "IMO 289 Environmental" claims to represent altitude in 0.1m steps, maxing out at 200m. This is plausible for a marine (as opposed to aeronautical) standard ... but 20m might also be reasonable, and cm would probably be more consistent with other heights.
"Table 47. Current flow (2D) report payload" claims to report current at depth in full meters, going down to 360m. That seems deeper than needed by anything that isn't both fixed and taking its own measurements. That said, 36.0 still seems too deep, and 3.61m seems too shallow and too fine-grained.
Same with table 48, 3D current flow, and table 49, horizontal current flow.
Table 50, sea state, seems plausible, except that by this time, I'm suspicious of all height or altitude measurements.
Table 53, air gap/air draught ... air draught was mentioned in an earlier issue, but air gap and forecast air gap seem similar.
Meteorological and Hydrological Data (IMO289) also reports current ... and suggests that 30m is sufficient.
Water Levels (Inland AIS) ... The cm seems sensible, because anything more precise is false precision. But it does allow up 80m difference from the baseline, which strikes me as ... not a situation where ships would be travelling on the river.