Was talking to a cruiser coming up from Panama and he was surprised at how much growth he sees on the bottom on the Pacific side as opposed to the Caribbean. I don't doubt you didn't see problems in your tropical waters but my experience in Pacific Mexico is lots of growth on all things under the waterline. It would be nice to have a reliable knot meter to compare with GPS to get and idea about current, as for speed when we travel at sea the current is pretty constant so using GPS for speed regarding sail trim is easy.
Tom Evans
Zihuatanejo Mexico