Any recommendations for training watches?

I have two.  A Garmin Swim 2 I use for swimming, and a Garmin Fenix 5s (?) I use for everything else.  The "multi-sport" watch won't measure heartrate while in swim mode.......which I did not know when I bought it.  It also lacks a stopwatch and a countdown timer (so if I have an interval that doesn't end in 5, like 36, 52, etc., I need a beep to say when to go).  Which is all to say that the "multi-sport" watch is pretty worthless.  But it does do stuff like track my VO2 Max, etc.  It really depends on what you are after.  I'm a swimmer who occasionally bikes or whatever else.  The cyclists who swim have a very different view than me (i.e. "if it isn't on Strava, it didn't happen").  The Swim 2 is a very useful tool to help me train.  It it not useful in broadcasting to my peer group that I worked harder than them 3 out of 7 days last week.

Can you tell I get annoyed at my tri-athlete peers who won't go if their watch isn't properly recording everything?

But seriously, if you are looking into a single device for multi-sport training, make sure that it will measure heartrate in the water.  Oh, and the calories burned algorithm is junk.  Doesn't matter if I do a fly set with my heartrate constantly exceeding my theoretical max, or if I tool around in the water, it gives me almost the exact same result per yard.  As is the yardage......any kick sets, underwater sets, or drills utilizing one arm at a time are not going to be picked up.  And the distance for open water swimming is highly suspect.  Easily 10% variable when comparing to other peers.  

Now that I think about it, the most effective watch I had was when I started a few years ago, just a Timex Ironman.  It had a stopwatch and a countdown timer.  No heartrate.  But honestly, anything beyond keeping up with intervals is more of a distraction than a training aid.

B5MN7, I have a Garmin 735 and it is great (thin, light, the battery that lasts 2 weeks, and it has all three sports).  
If you are already using an Apple Watch, it might be tough to let go of the integration to your (presumably) other apple products. The great thing about the Apple Watch is that you can not only have workout tracking but also guided workouts through the Swim.com app. USMS has a partnership with Swim.com and it integrates with the Workout Library. 
I have never tried Coros so can't speak to that. 

Thank you so much for all that great information! this helps so much!

Thank you so much! I'm not sure if it's just because my Apple Watch is older, but the swim.com app never really worked. It would glitch out so much, I was having so much trouble. maybe that's just how the app works? 

I have the latest Apple Watch. Loved my previous one but the new version pauses my workout for no reason. Almost as if the current causes it. 

I (re)started swimming 4 months back with Fitbit Charge 4, and then switched to the apple watch ultra. Having used fitbit/Samsung and apple ultra, I feel ultra is the best watch there is for swimmers. 

Stats are rich and detailed with heartbeat, auto-detected swim type, this watch is actually designed for Divers, with 3 days of battery-run and better integration with iPhone makes it stand out. 

https://www.apple.com/apple-watch-ultra/ 

I used to use an Apple watch until I got Ciye goggles. Now I  use both. The watch is still great to get my heart rate and cumulative number of laps—but nothing beats the goggles for splits. I did the one hour swim using the goggles and I knew with every turn my pace which was so helpful in keeping me on target. 

After a ton of research (Garmin could be a whole lot clearer on what their products offer/do not offer) and found the Garmin Forerunner 255 meets all my needs. Garmin doesn't make it clear, but you get all the functionality of the more expensive Fenix for half the cost! I get heart rate and training metrics, allowed to create workouts, and track my progress. This feature is not permitted with some of their other affordable products. Overall quite happy with this product.

I am a FORM goggle user.  They have a HUGE tri group and customized workouts you can download with the phone app geared around getting you in shape for your next race.  I'm not a triathlete with a fake hip.  I just swim competitively now and don't have a coach that fits my schedule at any one of the masters swim programs here in boiling hot outdoor pool Houston.   I'm now an ambassador after I successfully beat stage 4 throat cancer and used the goggles to get back into racing shape.  I have a code for 15% off using GRAHAM15 on their site.

I also wear a Garmin Venu 2 at the same time, it's terrible at counting laps etc.and never syncs up accurately with the goggles.  The FORM goggles do integrate with other Garmin watches along with Apple watches.  This might be the ticket for you.  I truly love these goggles although.