I have a hand held Garmin GPS76. It has Trip Computer which records Moving Average Speed,Moving Time,Overall Average Speed, Maximum Speed and Total Distance traveled. It also has Tracks.
Has anyone used this GPS when sailing, if not, would it be suitable for getting into GPS Speed sailing.

I've had a quick glance at an online description and it appears there probably isn't enough data memory.
I guess it depends what sort of gps speed sailing you want to get into. If you're only interested in how fast you're going, then the max speed readout will give you that.
But if you want to join the GPS team challenge, you need to be able to download and process the data.
The recommended GPS units for this are recommended here,

www.gpsteamchallenge.com.au/pages/rules

But this was written a few years ago now, (the GT11 and GT35 aren't in production, there are still a few GT31s in stock, but they have also come to production end).

You could try downloading a file from it and uploading to
www.ka72.com/

If you can successfully upload a few hours worth of 1hz or 2hz data, then it's a possibility.