Fans of location positioning systems (who isn't?) who also spend significant time in the water will appreciate the first ever GPS-enabled swim trackers ever seen. Hong Kong-based Platysens Limited, a two-year old startup, has developed a pair of useful swimming aids that not only keep swimmers on course, but also help to improve swimming performance.

The firm's two-piece Marlin device features a location mechanism that straps to the top of the head, while a second pod communicates with the user via bone conduction, bypassing the auditory canal. The gadget actually speaks to the swimmer, informing him/her of their pace without disrupting the swim stroke. Afterwards, the Marlin can be connected via Bluetooth to a smartphone, where an app enables swift data review.

In open water, the gadget makes use of GPS for pinpointing location, while indoors (where GPS may not be effective), a tiny accelerometer performs the job. Outside, the Marlin will inform the swimmer of time and distance measurements from and to the next waypoint, and issue warnings when the swimmer strays off course. In the pool, it counts laps, times, and stroke rates.

The combined unit weighs just 41 grams, and the components are relatively unobtrusive. Buttons control power/mode, start/pause/stop, and volume. Batteries are good for five to 10 hours, depending on the setting. It retails for about $150.

Quite apart from the Marlin, the company's Seal device is also a first in its genre - the only wearable gadget that actually provides a detailed analysis of "swimmetrics," or swim stroke performance. The unit's twin sensors are worn on the fingers of either hand, and work by measuring hand orientation and force exertion through the water.

After finishing, the data collected is sent for analysis by smartphone app, where vivid graphics help to better understand motion, rhythm, and left-right hand symmetry for improving stroke.

"Many people can swim, but few people can swim well," says Platysens R and D engineer Elliott Li. "The Marlin and Seal work as swim coach and swim guide, and are useful for beginners and serious swimmers alike."

A reviewer at DC Rainmaker, a gadget appraisal site, was impressed with the Marlin after putting it though a trial. "I like the assortment of buttons on it, and the audio feedback is super clear, both for general use confirmation (i.e. which mode you're in), but also while swimming openwater," he writes.

As of this writing, the Seal was still in development, slated for 2017 release.