NMEA 0183 standard Water Speed and Heading.
Syntax
$--VHW,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>*hh<CR><LF>
Fields
<1> Compass Heading, degrees True
<2> T = true
<3> Compass Heading, degrees Magnetic
<4> M = magnetic
<5> Water speed, knots
<6> N = knots
<7> Water speed, km/h
<8> K = km/h