TL/DR: Buy this one.
Long version: I bought and returned Casio G-Shocks with tidal functions.  Let me save you the research time. The G-Shocks use the lunitidal interval to calculate tidal information, which uses the lunar orbit to assume tide (moon overhead = high tide) and then a fixed delay (such as 4 hour delay due to underwater geography, other factors).  This is not accurate on the west coast of the US since the moon and sun share influence on the tides, and unless they are directly in line with each other (either one on either side of the earth, or both on one side of the earth) the actual tide time fluctuates as a harmonic (the orbiting bodies are out of phase) and therefore using a fixed variable offset is invalid.  This watch however uses pre-programmed information for the next 10 years, which we know will be accurate since it takes into account everything the lunitidal interval method does not, like the moon and sun being out of phase on the west coast.  So it's not "i like the way the g-shocks look, and the tidal info will be similar", no, it's "this watch will be spot-on every time and the g-shock will only be accurate once in a while".  This includes pre-programmed locations up and down the California coast, and you can do a custom location, such as "I will choose Humboldt Bay's data, then subtract 10 minutes from it to get the offset of the exact beach i want".  So, in closing, if you live on the west coast of the US, a lunitidal interval watch, such as the G-Shock, will not be accurate, whereas one with pre-programmed tide data, such as this one, will be spot-on.  Thanks for reading and I hope this helped save you some confusion and researching.